本系列学习笔记第3章
前言
打算把android基本知识点写一个系列，旨在把android基础书，例如《Android 第一行代码 第2版》、《爱上android》、《疯狂android讲义》等书的一些知识点记录一下，会持续更新内容，为了方便自己复习，也希望可以帮助到大家！
目录
1、TextView
2、Button
2.1 padding与margin属性的讲解
2.2 禁止Button中的所有英文字母自动进行大小写转换
2.3 点击事件的3种写法
2.3.1 匿名内部类
2.3.2 onClick属性
2.3.3 接口方式注册
3、EditText
4、ImageView
5、ProgressBar
6、AlertDialog
6.1 基本使用
6.2 例子的使用
7、ProgressDialog
8、常用的基本布局
8.1 线性布局
8.2 相对布局
8.3 帧布局
8.4 百分比布局
8.5 GridLayout（网格布局）
8.5.1 计算器界面例子
8.5.2 简单的登录界面例子
8.6 CoordinatorLayout
9、 创建组合自定义控件的流程
10、 ListView控件的基本使用
10.1 标准使用例子
10.2 长按点击事件和点击事件的事件传递
10.3 ListView的常用属性
11、GridView控件的基本使用
12、RecyclerView控件的基本使用
12.1 垂直布局
12.2 横向布局
12.3 瀑布流布局
12.4 Recycleview点击事件的另外一种写法以及数据添加、删除
13、Recycleview的综合练习
14、Toast的使用
14.1 Toast的创建方式
14.2 修改Toast的显示位置
14.3 自定义Toast布局
14.4 注意避免Toast因此的内存泄漏
15、Snackbar的使用
16、Lambda表达式
16.1 什么是Lambda表达式？
16.2 lambda表达式的基本格式
16.3 配置
17、ViewPager的简单使用
1、TextView
2、Button
2.1 padding与margin属性的讲解
android:layout_margin="10dp" //本元素离上下左右的距离
android:layout_marginTop="10dp" //顶部边缘离其它元素的距离
android:layout_marginBottom="10dp" //底部边缘离其它元素的距离
android:layout_marginRight="10dp" //右部边缘离其它元素的距离
android:layout_marginLeft="10dp" //左部边缘离其它元素的距离
android:layout_marginStart="10" //与layout_marginLeft效果一致
android:layout_marginEnd="10dp" //与layout_marginRight效果一致
android:padding="10dp" //元素内边距
android:paddingTop="10dp" //元素上边距
android:paddingBottom="10dp" //元素底边距
android:paddingLeft="10dp" //元素左边距
android:paddingRight="10dp" //元素右边距
image.png
2.2 禁止Button中的所有英文字母自动进行大小写转换
android:textAllCaps="false"
2.3 点击事件的3种写法
2.3.1 匿名内部类
Button button = (Button) findViewById(R.id.btn_1);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
}
});
2.3.2 onClick属性
public void buttonOnclic(View view){
Toast.makeText(this, "button", Toast.LENGTH_SHORT).show();
}
2.3.3 接口方式注册
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button = (Button) findViewById(R.id.btn_1);
button.setOnClickListener(this);
}
@Override
public void onClick(View view) {
switch (view.getId()){
case R.id.btn_1:
//处理的逻辑
break;
default:
break;
}
}
}
3、EditText
4、ImageView
scaleType选择的方式：
fitCenter:默认的方式，表示图片会填充控件，不会让图片变形，图片居中显示
fitXY:表示图片填充控件，但是允许图片拉伸
centerCrop:以填充ImageView控件为目的，将原图的中心对准ImageView的中心，等比例放大原图，直到填充ImageView为止（指的是把ImageView的宽和高都填满），原图超出ImageView的部分就会做裁剪
center:保持原图大小，显示在ImageView的中心，当原图的大小大于ImageView的大小，将会做裁剪处理
matrix:不改变原图的大小，从ImageView的左上角开始绘制原图，超出部分将会做裁剪处理
fitStart:把原图按比例扩大（缩小）到ImageView的高度，显示在ImageView的上部分
fitEnd:把原图按比例扩大（缩小）到ImageView的高度，显示在ImageView的下部分
centerInside:以原图完全显示为目的，将图片的内容完整居中显示，通过按比例缩小原图的宽高小于或者等于ImageView的宽高，如果原图的大小小于ImageView的大小，就显示不做处理
5、ProgressBar
默认样式
image.png
进度条样式
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
private ProgressBar progressBar;
private Button button;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = (Button) findViewById(R.id.btn_1);
progressBar = (ProgressBar) findViewById(R.id.pb);
button.setOnClickListener(this);
}
@Override
public void onClick(View view) {
switch (view.getId()){
case R.id.btn_1:
//处理的逻辑
int progress = progressBar.getProgress();
progress = progress + 10;
progressBar.setProgress(progress);
break;
default:
break;
}
}
}
image.png
android:visibility="visible" 表示控件可见
android:visibility="gone" 表示控件不可见，并且不占据布局中的位置和大小
android:visibility="invisible" 表示控件不可见，但是还占据布局中的位置和大小
6、AlertDialog
6.1 基本使用
AlertDialog可以在当前的页面弹出对话框，该对话框是置顶于所有的界面元素之上，能够屏蔽其它控件的交互能力
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
private Button button;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = (Button) findViewById(R.id.btn_1);
button.setOnClickListener(this);
}
@Override
public void onClick(View view) {
switch (view.getId()){
case R.id.btn_1:
initAlertDialog("警告","倒计时开始","确定","取消");
break;
default:
break;
}
}
/**
* 初始化AlertDialog
*/
private void initAlertDialog(String title,String msg,String positiveComfirmTip,String negativeComfirmTip) {
AlertDialog.Builder dialog = new AlertDialog.Builder(MainActivity.this);
dialog.setTitle(title);
dialog.setMessage(msg);
dialog.setCancelable(false);
dialog.setPositiveButton(positiveComfirmTip, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
}
});
dialog.setNegativeButton(negativeComfirmTip, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
}
});
dialog.show();
}
}
image.png
6.2 例子的使用
dialog_custom.xml文件
activity_dialog_demo.xml文件
DialogDemoActivity.java文件
public class DialogDemoActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_dialog_demo);
}
// 一般对话框
public void normalDialog(View v) {
//先得到构造器
AlertDialog.Builder builder = new AlertDialog.Builder(this);
//设置标题
builder.setTitle("提示");
builder.setMessage("是否确认退出"); //设置内容
builder.setIcon(R.mipmap.ic_launcher); //自定义图标
builder.setCancelable(false); //设置是否能点击，对话框的其他区域取消
//设置其确认按钮和监听事件
builder.setPositiveButton("确认", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
//设置其取消按钮和监听事件
builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
//设置其忽略按钮和监听事件
builder.setNeutralButton("忽略", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
// 下面两行代码 可以合成一行 builder.show()
Dialog dialog=builder.create(); //创建对话框
dialog.show(); //显示对话框
}
//列表对话框
public void listDialog(View v) {
final String items[] = {"AAA", "BBB", "CCC"};
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("提示"); //设置标题
builder.setIcon(R.mipmap.ic_launcher);//设置图标，图片id即可
//设置列表显示，注意设置了列表显示就不要设置builder.setMessage()了，否则列表不起作用。
builder.setItems(items, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
Toast.makeText(getApplicationContext(), items[which], Toast.LENGTH_SHORT).show();
}
});
builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
Toast.makeText(getApplicationContext(), "确定", Toast.LENGTH_SHORT).show();
}
});
builder.create().show();
}
// 单选按钮对话框
public void singleDialog(View v) {
final String items[] = {"男", "未知", "女"};
AlertDialog.Builder builder = new AlertDialog.Builder(this);
//设置标题
builder.setTitle("提示");
//设置图标，图片id即可
builder.setIcon(R.mipmap.ic_launcher);
//设置单选按钮
// items 为列表项
// 0 为默认选中第一个
// 第三个参数是监听器
builder.setSingleChoiceItems(items, -1, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Toast.makeText(getApplicationContext(), items[which], Toast.LENGTH_SHORT).show();
}
});
// 设置监听器
builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
Toast.makeText(getApplicationContext(), "确定", Toast.LENGTH_SHORT).show();
}
});
builder.create().show();
}
// 多选对话框
public void mulDialog(View v) {
final String items[] = {"篮球", "足球", "排球"};
final boolean selected[] = {true, false, true};
AlertDialog.Builder builder = new AlertDialog.Builder(this); //先得到构造器
builder.setTitle("爱好"); //设置标题
builder.setIcon(R.mipmap.ic_launcher);//设置图标，图片id即可
// 参数一：列表项
// 参数二：默认打勾的
// 参数三：监听器
builder.setMultiChoiceItems(items, selected,
new DialogInterface.OnMultiChoiceClickListener() {
@Override
public void onClick(DialogInterface dialog, int which, boolean isChecked) {
// dialog.dismiss();
Toast.makeText(getApplicationContext(),
items[which] + isChecked, Toast.LENGTH_SHORT).show();
}
});
// 确认按钮
builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
Toast.makeText(getApplicationContext(), "确定", Toast.LENGTH_SHORT).show();
//android会自动根据你选择的改变selected数组的值。
for (int i = 0; i < selected.length; i++) {
Log.i("mulDialog", "" + selected[i]);
}
}
});
builder.create().show();
}
// 自定义对话框
public void customDialog(View v) {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
//设置标题
builder.setTitle("自定义dialog");
//设置图标，图片id即可
builder.setIcon(R.mipmap.ic_launcher);
// 载入布局
LayoutInflater inflater = getLayoutInflater();
View layout = inflater.inflate(R.layout.dialog_custom, null);
builder.setView(layout);
// 初始化自定义布局中的控件, 因为控件在自定义layout中, 必须用layout.findViewByID
EditText editText_name = (EditText) layout.findViewById(R.id.editText_name);
EditText editText_password = (EditText) layout.findViewById(R.id.editText_password);
// 确认按钮
builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
// 显示
builder.create().show();
}
}
image.png
7、ProgressDialog
与AlertDialog有点类似，不同的就是ProgressDialog会显示一个进度条，一般表示当前操作是耗时的
/**
* 初始化initProgressDialog
*/
private void initProgressDialog(String title,String message) {
ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
progressDialog.setTitle(title);
progressDialog.setMessage(message);
progressDialog.setCancelable(true);
progressDialog.show();
}
image.png
8、常用的基本布局
image.png
image.png
8.1 线性布局
android:orientation="vertical" 指定线性垂直布局
android:orientation="horizontal" 指定线性水平布局
android:layout_weight="" 线性布局很重要的一个特性，可以让控件按照屏幕的比例来缩放，是屏幕适配一个很好的应用
8.2 相对布局
与父布局相关的布局属性
android:layout_centerInParent="true" //位于父布局的中央
android:layout_alignParentLeft="true"//位于父布局的左边
android:layout_alignParentRight="true"//位于父布局的右边
android:layout_alignParentBottom="true"//位于父布局的底部
android:layout_alignParentTop="true"//位于父布局的顶部
与其它控件相关的布局属性
android:layout_above="@id/btn_1" //位于某个控件的上面
android:layout_below="@id/btn_1" //位于某个控件的下面
android:layout_toLeftOf="@id/btn_1"//位于某个控件的左边
android:layout_toRightOf="@id/btn_1"//位于某个控件的右边
image.png
image.png
image.png
8.3 帧布局
这种布局没有方便的地位方式，所有的控件都会默认摆放在布局的左上角，经常结合碎片来应用或者某些app上面的引导页也可以用帧布局来实现
image.png
8.4 百分比布局
为了解决相对布局和帧布局在按照比例来指定控件大小的缺陷，从而引入了百分比布局
image.png
image.png
8.5 GridLayout（网格布局）
1）和LinearLayout一样有vertical（垂直）和horizontal（水平）这两种方式
2）设置android:columnCount="4"列属性后，子控件会自动进行换行排列
3）指定某控件在固定的行和列：
android:layout_column="0" 在第一列开始
android:layout_row="0" 在第一行开始
8.5.1 计算器界面例子
image.png
8.5.2 简单的登录界面例子
8.6 CoordinatorLayout
image.png
9、 创建组合自定义控件的流程
根据需求写出组合控件的布局：title.xml
自定义控件编码：TitleLayout.java
public class TitleLayout extends LinearLayout {
public TitleLayout(Context context, AttributeSet attrs) {
super(context, attrs);
View rootView = LayoutInflater.from(context).inflate(R.layout.title, this);
Button titleBack = (Button) rootView.findViewById(R.id.title_back);
Button titleEdit = (Button) rootView.findViewById(R.id.title_edit);
titleBack.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
((Activity) getContext()).finish();
}
});
titleEdit.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(getContext(), "You clicked Edit button",
Toast.LENGTH_SHORT).show();
}
});
}
}
布局上引用
主代码中显示
public class Main2Activity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
ActionBar actionBar = getSupportActionBar();
if (actionBar != null){
actionBar.hide();
}
}
}
image.png
10、 ListView控件的基本使用
10.1 标准使用例子
数据实体类
public class Fruit {
private String name;
private int imageId;
public Fruit(String name, int imageId) {
this.name = name;
this.imageId = imageId;
}
public String getName() {
return name;
}
public int getImageId() {
return imageId;
}
}
列表Item的布局
数据适配器
public class FruitAdapter extends ArrayAdapter {
private int resourceId;
public FruitAdapter(@NonNull Context context, int resource, @NonNull List objects) {
super(context, resource, objects);
this.resourceId = resource;
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
Fruit fruit = getItem(position);
View view = null;
ViewHolder viewHolder = null;
if (convertView == null){
view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);
viewHolder = new ViewHolder();
viewHolder.fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
viewHolder.fruitName = (TextView) view.findViewById(R.id.fruit_name);
view.setTag(viewHolder);
}else {
view = convertView;
viewHolder = (ViewHolder) view.getTag();
}
viewHolder.fruitImage.setImageResource(fruit.getImageId());
viewHolder.fruitName.setText(fruit.getName());
return view;
}
class ViewHolder{
ImageView fruitImage;
TextView fruitName;
}
}
界面主布局
主界面实现代码
public class ListViewActivity extends AppCompatActivity {
private List fruitList = new ArrayList<>();
private ListView listView;
private Context context;
private FruitAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_list_view);
initView();
initFruits();
initListView();
}
private void initView() {
context = this;
listView = (ListView) findViewById(R.id.list_view);
}
private void initListView() {
adapter = new FruitAdapter(context, R.layout.fruit_item,fruitList);
listView.setAdapter(adapter);
//ListView的点击事件
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView adapterView, View view, int i, long l) {
Fruit fruit = fruitList.get(i);
Toast.makeText(context, "你选择的是"+fruit.getName(), Toast.LENGTH_SHORT).show();
}
});
//ListView的长按点击事件
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView adapterView, View view, int position, long l) {
fruitList.remove(position);
adapter.notifyDataSetChanged();
return true;
}
});
}
private void initFruits() {
for (int i = 0; i < 2; i++) {
Fruit apple = new Fruit("Apple", R.drawable.apple_pic);
fruitList.add(apple);
Fruit banana = new Fruit("Banana", R.drawable.banana_pic);
fruitList.add(banana);
Fruit orange = new Fruit("Orange", R.drawable.orange_pic);
fruitList.add(orange);
Fruit watermelon = new Fruit("Watermelon", R.drawable.watermelon_pic);
fruitList.add(watermelon);
Fruit pear = new Fruit("Pear", R.drawable.pear_pic);
fruitList.add(pear);
Fruit grape = new Fruit("Grape", R.drawable.grape_pic);
fruitList.add(grape);
Fruit pineapple = new Fruit("Pineapple", R.drawable.pineapple_pic);
fruitList.add(pineapple);
Fruit strawberry = new Fruit("Strawberry", R.drawable.strawberry_pic);
fruitList.add(strawberry);
Fruit cherry = new Fruit("Cherry", R.drawable.cherry_pic);
fruitList.add(cherry);
Fruit mango = new Fruit("Mango", R.drawable.mango_pic);
fruitList.add(mango);
}
}
}
image.png
10.2 长按点击事件和点击事件的事件传递
image.png
10.3 ListView的常用属性
android:divider="" //设置分割线的颜色或者指定分割线的图片
android:dividerHeight="" //设置分割线的高度
android:scrollbars="none" //隐藏滚动条
11、GridView控件的基本使用
image.png
Fruit,java文件
public class Fruit {
private String name;
private int imageId;
public Fruit(String name, int imageId) {
this.name = name;
this.imageId = imageId;
}
public String getName() {
return name;
}
public int getImageId() {
return imageId;
}
}
gv_fruit_item.xml文件
FruitAdapter.java文件
public class FruitAdapter extends ArrayAdapter {
private int resourceId;
public FruitAdapter(@NonNull Context context, int resource, @NonNull List objects) {
super(context, resource, objects);
this.resourceId = resource;
}
@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
Fruit fruit = getItem(position);
View view = null;
ViewHolder viewHolder = null;
if (convertView == null){
view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);
viewHolder = new ViewHolder();
viewHolder.fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
viewHolder.fruitName = (TextView) view.findViewById(R.id.fruit_name);
view.setTag(viewHolder);
}else {
view = convertView;
viewHolder = (ViewHolder) view.getTag();
}
viewHolder.fruitImage.setImageResource(fruit.getImageId());
viewHolder.fruitName.setText(fruit.getName());
return view;
}
class ViewHolder{
ImageView fruitImage;
TextView fruitName;
}
}
activity_grid_view.xml文件
GridViewActivity.java文件
public class GridViewActivity extends AppCompatActivity {
private List fruitList = new ArrayList<>();
private GridView gvView;
private Context context;
private FruitAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_grid_view);
initView();
initFruits();
initListView();
}
private void initView() {
context = this;
gvView = (GridView) findViewById(R.id.gv);
}
private void initListView() {
adapter = new FruitAdapter(context, R.layout.gv_fruit_item,fruitList);
gvView.setAdapter(adapter);
gvView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView adapterView, View view, int i, long l) {
Fruit fruit = fruitList.get(i);
Toast.makeText(context, "你选择的是"+fruit.getName(), Toast.LENGTH_SHORT).show();
}
});
gvView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView adapterView, View view, int position, long l) {
fruitList.remove(position);
adapter.notifyDataSetChanged();
return true;
}
});
}
private void initFruits() {
for (int i = 0; i < 2; i++) {
Fruit apple = new Fruit("Apple", R.drawable.apple_pic);
fruitList.add(apple);
Fruit banana = new Fruit("Banana", R.drawable.banana_pic);
fruitList.add(banana);
Fruit orange = new Fruit("Orange", R.drawable.orange_pic);
fruitList.add(orange);
Fruit watermelon = new Fruit("Watermelon", R.drawable.watermelon_pic);
fruitList.add(watermelon);
Fruit pear = new Fruit("Pear", R.drawable.pear_pic);
fruitList.add(pear);
Fruit grape = new Fruit("Grape", R.drawable.grape_pic);
fruitList.add(grape);
Fruit pineapple = new Fruit("Pineapple", R.drawable.pineapple_pic);
fruitList.add(pineapple);
Fruit strawberry = new Fruit("Strawberry", R.drawable.strawberry_pic);
fruitList.add(strawberry);
Fruit cherry = new Fruit("Cherry", R.drawable.cherry_pic);
fruitList.add(cherry);
Fruit mango = new Fruit("Mango", R.drawable.mango_pic);
fruitList.add(mango);
}
}
}
image.png
11、 RecyclerView控件的基本使用
image.png
image.png
11.1 垂直布局
数据实体类
public class Fruit {
private String name;
private int imageId;
public Fruit(String name, int imageId) {
this.name = name;
this.imageId = imageId;
}
public String getName() {
return name;
}
public int getImageId() {
return imageId;
}
}
列表Item布局(注意这个和ListView的区别)
数据适配器
public class FruitsAdapter extends RecyclerView.Adapter {
private List mFruitList;
public FruitsAdapter(List mFruitList) {
this.mFruitList = mFruitList;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item,parent,false);
ViewHolder viewHolder = new ViewHolder(view);
return viewHolder;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Fruit fruit = mFruitList.get(position);
holder.fruitImage.setImageResource(fruit.getImageId());
holder.fruitName.setText(fruit.getName());
}
@Override
public int getItemCount() {
return mFruitList.size();
}
static class ViewHolder extends RecyclerView.ViewHolder{
ImageView fruitImage;
TextView fruitName;
public ViewHolder(View itemView) {
super(itemView);
fruitImage = (ImageView)itemView.findViewById(R.id.fruit_image);
fruitName = (TextView)itemView.findViewById(R.id.fruit_name);
}
}
}
主界面布局
主界面逻辑代码
public class RecyclerViewActivity extends AppCompatActivity {
private RecyclerView recyclerView;
private List fruitList = new ArrayList<>();
private Context context;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recycler_view);
initView();
initFruits();
initRecycleView();
}
private void initView() {
context = this;
recyclerView = (RecyclerView) findViewById(R.id.rv);
}
private void initFruits() {
for (int i = 0; i < 2; i++) {
Fruit apple = new Fruit("Apple", R.drawable.apple_pic);
fruitList.add(apple);
Fruit banana = new Fruit("Banana", R.drawable.banana_pic);
fruitList.add(banana);
Fruit orange = new Fruit("Orange", R.drawable.orange_pic);
fruitList.add(orange);
Fruit watermelon = new Fruit("Watermelon", R.drawable.watermelon_pic);
fruitList.add(watermelon);
Fruit pear = new Fruit("Pear", R.drawable.pear_pic);
fruitList.add(pear);
Fruit grape = new Fruit("Grape", R.drawable.grape_pic);
fruitList.add(grape);
Fruit pineapple = new Fruit("Pineapple", R.drawable.pineapple_pic);
fruitList.add(pineapple);
Fruit strawberry = new Fruit("Strawberry", R.drawable.strawberry_pic);
fruitList.add(strawberry);
Fruit cherry = new Fruit("Cherry", R.drawable.cherry_pic);
fruitList.add(cherry);
Fruit mango = new Fruit("Mango", R.drawable.mango_pic);
fruitList.add(mango);
}
}
private void initRecycleView() {
FruitsAdapter adapter = new FruitsAdapter(fruitList);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(context);
recyclerView.setLayoutManager(linearLayoutManager);
recyclerView.setAdapter(adapter);
}
}
image.png
11.2 横向布局
修改上面的代码实现横向布局
public class RecyclerViewActivity extends AppCompatActivity {
private RecyclerView recyclerView;
private List fruitList = new ArrayList<>();
private Context context;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recycler_view);
initView();
initFruits();
initRecycleView();
}
private void initView() {
context = this;
recyclerView = (RecyclerView) findViewById(R.id.rv);
}
private void initFruits() {
for (int i = 0; i < 2; i++) {
Fruit apple = new Fruit("Apple", R.drawable.apple_pic);
fruitList.add(apple);
Fruit banana = new Fruit("Banana", R.drawable.banana_pic);
fruitList.add(banana);
Fruit orange = new Fruit("Orange", R.drawable.orange_pic);
fruitList.add(orange);
Fruit watermelon = new Fruit("Watermelon", R.drawable.watermelon_pic);
fruitList.add(watermelon);
Fruit pear = new Fruit("Pear", R.drawable.pear_pic);
fruitList.add(pear);
Fruit grape = new Fruit("Grape", R.drawable.grape_pic);
fruitList.add(grape);
Fruit pineapple = new Fruit("Pineapple", R.drawable.pineapple_pic);
fruitList.add(pineapple);
Fruit strawberry = new Fruit("Strawberry", R.drawable.strawberry_pic);
fruitList.add(strawberry);
Fruit cherry = new Fruit("Cherry", R.drawable.cherry_pic);
fruitList.add(cherry);
Fruit mango = new Fruit("Mango", R.drawable.mango_pic);
fruitList.add(mango);
}
}
private void initRecycleView() {
FruitsAdapter adapter = new FruitsAdapter(fruitList);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(context);
linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
recyclerView.setLayoutManager(linearLayoutManager);
//GridView布局
//recyclerView.setLayoutManager(new GridLayoutManager(this,3));
recyclerView.setAdapter(adapter);
}
}
image.png
image.png
11.3 瀑布流布局
public class FruitsAdapter extends RecyclerView.Adapter {
private List mFruitList;
public FruitsAdapter(List mFruitList) {
this.mFruitList = mFruitList;
}
@Override
public ViewHolder onCreateViewHolder(final ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item,parent,false);
final ViewHolder viewHolder = new ViewHolder(view);
viewHolder.fruitView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
int position = viewHolder.getAdapterPosition();
Fruit fruit = mFruitList.get(position);
Toast.makeText(view.getContext(), "你点击了整个View:"+fruit.getName(), Toast.LENGTH_SHORT).show();
}
});
viewHolder.fruitImage.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
int position = viewHolder.getAdapterPosition();
Fruit fruit = mFruitList.get(position);
Toast.makeText(view.getContext(), "你点击了图片:"+fruit.getName(), Toast.LENGTH_SHORT).show();
}
});
return viewHolder;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Fruit fruit = mFruitList.get(position);
holder.fruitImage.setImageResource(fruit.getImageId());
holder.fruitName.setText(fruit.getName());
}
@Override
public int getItemCount() {
return mFruitList.size();
}
static class ViewHolder extends RecyclerView.ViewHolder{
View fruitView;
ImageView fruitImage;
TextView fruitName;
public ViewHolder(View itemView) {
super(itemView);
fruitView = itemView;
fruitImage = (ImageView)itemView.findViewById(R.id.fruit_image);
fruitName = (TextView)itemView.findViewById(R.id.fruit_name);
}
}
}
public class RecyclerViewActivity extends AppCompatActivity {
private static final String TAG = RecyclerViewActivity.class.getSimpleName();
private RecyclerView recyclerView;
private List fruitList = new ArrayList<>();
private Context context;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recycler_view);
initView();
initFruits();
initRecycleView();
}
private void initView() {
context = this;
recyclerView = (RecyclerView) findViewById(R.id.rv);
}
private void initFruits() {
for (int i = 0; i < 2; i++) {
Fruit apple = new Fruit(getRandomLengthName("Apple"), R.drawable.apple_pic);
fruitList.add(apple);
Fruit banana = new Fruit(getRandomLengthName("Banana"), R.drawable.banana_pic);
fruitList.add(banana);
Fruit orange = new Fruit(getRandomLengthName("Orange"), R.drawable.orange_pic);
fruitList.add(orange);
Fruit watermelon = new Fruit(getRandomLengthName("Watermelon"), R.drawable.watermelon_pic);
fruitList.add(watermelon);
Fruit pear = new Fruit(getRandomLengthName("Pear"), R.drawable.pear_pic);
fruitList.add(pear);
Fruit grape = new Fruit(getRandomLengthName("Grape"), R.drawable.grape_pic);
fruitList.add(grape);
Fruit pineapple = new Fruit(getRandomLengthName("Pineapple"), R.drawable.pineapple_pic);
fruitList.add(pineapple);
Fruit strawberry = new Fruit(getRandomLengthName("Strawberry"), R.drawable.strawberry_pic);
fruitList.add(strawberry);
Fruit cherry = new Fruit(getRandomLengthName("Cherry"), R.drawable.cherry_pic);
fruitList.add(cherry);
Fruit mango = new Fruit(getRandomLengthName("Mango"), R.drawable.mango_pic);
fruitList.add(mango);
}
}
private void initRecycleView() {
FruitsAdapter adapter = new FruitsAdapter(fruitList);
StaggeredGridLayoutManager linearLayoutManager = new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL);
recyclerView.setLayoutManager(linearLayoutManager);
recyclerView.setAdapter(adapter);
}
private String getRandomLengthName(String name){
Random random = new Random();
int length = random.nextInt(20) + 1;
Log.d(TAG,"length========="+length);
StringBuilder builder = new StringBuilder();
for (int i = 0; i < length; i++) {
builder.append(name);
}
return builder.toString();
}
}
image.png
11.4 Recycleview点击事件的另外一种写法以及数据添加、删除
FruitsAdapter2.java 文件
public class FruitsAdapter2 extends RecyclerView.Adapter implements View.OnClickListener{
private static final String TAG = FruitsAdapter2.class.getSimpleName();
private List mFruitList;
public FruitsAdapter2(List mFruitList) {
this.mFruitList = mFruitList;
}
public OnRecyclerViewOnItemClickListener mOnItemClickListener;
public void setOnRecyclerViewOnItemClickListener(OnRecyclerViewOnItemClickListener onRecyclerViewOnItemClickListener) {
this.mOnItemClickListener = onRecyclerViewOnItemClickListener;
}
@Override
public ViewHolder onCreateViewHolder(final ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item,parent,false);
final ViewHolder viewHolder = new ViewHolder(view);
viewHolder.fruitView.setOnClickListener(this);
return viewHolder;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Fruit fruit = mFruitList.get(position);
holder.fruitImage.setImageResource(fruit.getImageId());
holder.fruitName.setText(fruit.getName());
holder.fruitView.setTag(position);
}
@Override
public int getItemCount() {
return mFruitList.size();
}
static class ViewHolder extends RecyclerView.ViewHolder{
View fruitView;
ImageView fruitImage;
TextView fruitName;
public ViewHolder(View itemView) {
super(itemView);
fruitView = itemView;
fruitImage = (ImageView)itemView.findViewById(R.id.fruit_image);
fruitName = (TextView)itemView.findViewById(R.id.fruit_name);
}
}
@Override
public void onClick(View view) {
if (mOnItemClickListener != null){
int position = (int) view.getTag();
Fruit fruit = mFruitList.get(position);
mOnItemClickListener.onItemClick(view,fruit,position);
}
}
public void addItem(int position,Fruit fruit){
if (mFruitList != null){
mFruitList.add(position,fruit);
notifyItemInserted(position);
notifyItemChanged(position); //通知重新绑定某一个Item的数据与界面
}
}
public void deleteItem(int position,Fruit fruit){
if (mFruitList != null && mFruitList.size() > 0){
Log.d(TAG," mFruitList.size()==========="+ mFruitList.size());
Log.d(TAG,"position==========="+position);
mFruitList.remove(position);
notifyDataSetChanged(); //通知重新绑定所有数据与界面
}
}
public static interface OnRecyclerViewOnItemClickListener{
void onItemClick(View itemView,Fruit item,int position);
}
}
RecyclerViewActivity.java文件
public class RecyclerViewActivity extends AppCompatActivity {
private static final String TAG = RecyclerViewActivity.class.getSimpleName();
private RecyclerView recyclerView;
private List fruitList = new ArrayList<>();
private Context context;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recycler_view);
initView();
initFruits();
initRecycleView();
}
private void initView() {
context = this;
recyclerView = (RecyclerView) findViewById(R.id.rv);
}
private void initFruits() {
for (int i = 0; i < 2; i++) {
Fruit apple = new Fruit(getRandomLengthName("Apple"), R.drawable.apple_pic);
fruitList.add(apple);
Fruit banana = new Fruit(getRandomLengthName("Banana"), R.drawable.banana_pic);
fruitList.add(banana);
Fruit orange = new Fruit(getRandomLengthName("Orange"), R.drawable.orange_pic);
fruitList.add(orange);
Fruit watermelon = new Fruit(getRandomLengthName("Watermelon"), R.drawable.watermelon_pic);
fruitList.add(watermelon);
Fruit pear = new Fruit(getRandomLengthName("Pear"), R.drawable.pear_pic);
fruitList.add(pear);
Fruit grape = new Fruit(getRandomLengthName("Grape"), R.drawable.grape_pic);
fruitList.add(grape);
Fruit pineapple = new Fruit(getRandomLengthName("Pineapple"), R.drawable.pineapple_pic);
fruitList.add(pineapple);
Fruit strawberry = new Fruit(getRandomLengthName("Strawberry"), R.drawable.strawberry_pic);
fruitList.add(strawberry);
Fruit cherry = new Fruit(getRandomLengthName("Cherry"), R.drawable.cherry_pic);
fruitList.add(cherry);
Fruit mango = new Fruit(getRandomLengthName("Mango"), R.drawable.mango_pic);
fruitList.add(mango);
}
}
private void initRecycleView() {
final FruitsAdapter2 adapter = new FruitsAdapter2(fruitList);
// StaggeredGridLayoutManager linearLayoutManager = new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL);
recyclerView.setLayoutManager(new GridLayoutManager(this,3));
recyclerView.setAdapter(adapter);
adapter.setOnRecyclerViewOnItemClickListener(new FruitsAdapter2.OnRecyclerViewOnItemClickListener() {
@Override
public void onItemClick(View itemView, Fruit item, int position) {
//模拟删除数据
// adapter.deleteItem(position,item);
//模拟添加数据
Fruit fruit = new Fruit("水蜜桃",R.drawable.apple_pic);
//表示要插入数据的位置
int insertPosition = 0;
if (fruitList != null){
int size = fruitList.size();
insertPosition = size;
}
adapter.addItem(insertPosition,fruit);
recyclerView.scrollToPosition(fruitList.size()-1);
}
});
}
private String getRandomLengthName(String name){
Random random = new Random();
int length = random.nextInt(20) + 1;
Log.d(TAG,"length========="+length);
StringBuilder builder = new StringBuilder();
for (int i = 0; i < length; i++) {
builder.append(name);
}
return builder.toString();
}
}
image.png
13、Recycleview的综合练习
数据实体类
public class Msg {
public static final int TYPE_RECEIVED = 0;
public static final int TYPE_SENT = 1;
private String content;
private int type;
public Msg(String content, int type) {
this.content = content;
this.type = type;
}
public String getContent() {
return content;
}
public int getType() {
return type;
}
}
列表Item布局
数据适配器
public class MsgAdapter extends RecyclerView.Adapter {
private List mMsgList;
public MsgAdapter(List msgList) {
mMsgList = msgList;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.msg_item, parent, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Msg msg = mMsgList.get(position);
if (msg.getType() == Msg.TYPE_RECEIVED) {
// 如果是收到的消息，则显示左边的消息布局，将右边的消息布局隐藏
holder.leftLayout.setVisibility(View.VISIBLE);
holder.rightLayout.setVisibility(View.GONE);
holder.leftMsg.setText(msg.getContent());
} else if(msg.getType() == Msg.TYPE_SENT) {
// 如果是发出的消息，则显示右边的消息布局，将左边的消息布局隐藏
holder.rightLayout.setVisibility(View.VISIBLE);
holder.leftLayout.setVisibility(View.GONE);
holder.rightMsg.setText(msg.getContent());
}
}
@Override
public int getItemCount() {
return mMsgList.size();
}
static class ViewHolder extends RecyclerView.ViewHolder {
LinearLayout leftLayout;
LinearLayout rightLayout;
TextView leftMsg;
TextView rightMsg;
public ViewHolder(View view) {
super(view);
leftLayout = (LinearLayout) view.findViewById(R.id.left_layout);
rightLayout = (LinearLayout) view.findViewById(R.id.right_layout);
leftMsg = (TextView) view.findViewById(R.id.left_msg);
rightMsg = (TextView) view.findViewById(R.id.right_msg);
}
}
}
主界面布局
主界面逻辑代码
public class ChatActivity extends AppCompatActivity {
private List msgList = new ArrayList();
private EditText inputText;
private Button send;
private RecyclerView msgRecyclerView;
private MsgAdapter adapter;
private Context context;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_chat);
initView();
initChatData();
initRecyclerView();
initListener();
}
private void initListener() {
send.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String content = inputText.getText().toString();
if (!"".equals(content)) {
Msg msg = new Msg(content, Msg.TYPE_SENT);
msgList.add(msg);
adapter.notifyItemInserted(msgList.size() - 1); // 当有新消息时，刷新ListView中的显示
msgRecyclerView.scrollToPosition(msgList.size() - 1); // 将ListView定位到最后一行
inputText.setText(""); // 清空输入框中的内容
}
}
});
}
private void initRecyclerView() {
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
msgRecyclerView.setLayoutManager(layoutManager);
adapter = new MsgAdapter(msgList);
msgRecyclerView.setAdapter(adapter);
}
private void initChatData() {
Msg msg1 = new Msg("Hello guy.", Msg.TYPE_RECEIVED);
msgList.add(msg1);
Msg msg2 = new Msg("Hello. Who is that?", Msg.TYPE_SENT);
msgList.add(msg2);
Msg msg3 = new Msg("This is Tom. Nice talking to you. ", Msg.TYPE_RECEIVED);
msgList.add(msg3);
}
private void initView() {
context = this;
inputText = (EditText) findViewById(R.id.input_text);
send = (Button) findViewById(R.id.send);
msgRecyclerView = (RecyclerView) findViewById(R.id.msg_recycler_view);
}
}
image.png
14、Toast的使用
14.1 Toast的创建方式
//创建Toast的两种方式
//直接使用字符串
Toast.makeText(mContext, "", Toast.LENGTH_SHORT).show();
//引用资源字符串
Toast.makeText(mContext, R.string.app_name, Toast.LENGTH_SHORT).show();
14.2 修改Toast的显示位置
第一种方法：toast.setMargin(float horizontalMargin, float verticalMargin)
第二种方法：toast.setGravity(int gravity, int xOffset, int yOffset);
14.3 自定义Toast布局
private void showToast(Context context){
Toast toast = new Toast(context);
//代码创建自定义样式
ImageView iv = new ImageView(context);
iv.setImageResource(R.mipmap.ic_launcher);
LinearLayout linearLayout = new LinearLayout(context);
linearLayout.setOrientation(LinearLayout.HORIZONTAL);
linearLayout.addView(iv);
//引用布局的方式
// LayoutInflater inflater = getLayoutInflater();
// View inflate = inflater.inflate(R.layout.toast, null);
// toast.setView(inflate);
toast.setDuration(Toast.LENGTH_SHORT);
toast.setView(linearLayout);
}
14.4 注意避免Toast因此的内存泄漏
什么是内存泄漏？
就是该回收的内存由于种种原因没有被回收，还驻留在内存中。说白了就是站着茅坑不拉屎，很容易导致厕所满员了，着急上厕所的人上不了。
如下的代码：
Toast.makeText(mContext, "", Toast.LENGTH_SHORT).show();
如果Toast在没有消失之前，点击返回键结束了页面，因为toast持有了Activity的实例，该Activity没有真正销毁，这个Activity就会造成内存泄漏。
解决方法：
Toast.makeText(getApplicationContext(), "", Toast.LENGTH_SHORT).show();
15、Snackbar的使用
public class MainActivity extends AppCompatActivity {
private FloatingActionButton flbActionBar;
private CoordinatorLayout rootView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
rootView = (CoordinatorLayout) findViewById(R.id.rootview);
flbActionBar = (FloatingActionButton) findViewById(R.id.flb);
flbActionBar.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(rootView,"Test! Test!",Snackbar.LENGTH_SHORT)
.setAction("确定", new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(MainActivity.this, "点击了确定按钮！", Toast.LENGTH_SHORT).show();
}
})
.show();
}
});
}
}
image.png
注意点：
1）、make方法的第一个参数是一个View，不是上下文Context对象，任何一个View都可以，官方推荐使用CoordinatorLayout，这样做有俩个好处:
1：用户右滑可以消除Snackbar
2：当Snackbar出现时，布局会移动一下UI元素，比如右下角的浮动按钮在Snackbar出现时，会向上移动
2）、View不一定是要是CoordinatorLayout，该方法触发时会一步一步向上查找，有没有CoordinatorLayout，如果找到顶层还没有就停止查找，所以最好是用CoordinatorLayout布局，这样就不用系统一步一步去查找
3）、如果布局是已经写好了的，没有CoordinatorLayout，可以在最外层加一个CoordinatorLayout，CoordinatorLayout相当于一个超级帧布局
16、Lambda表达式
16.1 什么是Lambda表达式？
该表达式允许我们将行为传递函数中，之前我们将行为传递函数中采用的是匿名内部类，该方法导致函数最重要的部分夹在中间，不过突出，例如：
flbActionBar.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
showView();
}
});
采用Lambda表达式后，就是一行代码
flbActionBar.setOnClickListener(v -> showView());
16.2 lambda表达式的基本格式
() -> {}
有下面三种表达形式：
1、（params） -> expressions
2、（params） -> statement
3、（params） -> {statement}
16.3 配置
//编译支持java8
compileOptions{
sourceCompatibility 1.8
targetCompatibility 1.8
//或者写成下面这个样子
// sourceCompatibility JavaVersion.VERSION_1_8
// targetCompatibility JavaVersion.VERSION_1_8
}
17、ViewPager的简单使用
创建3个view布局
layou_view_one.xml文件
layou_view_two.xml文件
layou_view_three.xml文件
activity_view_pager.xml文件
ViewPagerAdapter.java文件
public class ViewPagerAdapter extends PagerAdapter {
private List mViewList;
public ViewPagerAdapter(List viewList) {
this.mViewList = viewList;
}
@Override
public int getCount() {
return mViewList.size();
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
View view = mViewList.get(position);
container.addView(view);
return view;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
View view = mViewList.get(position);
container.removeView(view);
}
}
ViewPagerActivity.java文件
public class ViewPagerActivity extends AppCompatActivity {
private Context mContext;
private ViewPager viewPager;
private List mListView = new ArrayList<>();
private LayoutInflater inflater;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_view_pager);
initView();
initData();
initViewPager();
}
private void initViewPager() {
ViewPagerAdapter adapter = new ViewPagerAdapter(mListView);
viewPager.setAdapter(adapter);
viewPager.setOffscreenPageLimit(mListView.size());
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
}
private void initData() {
inflater = LayoutInflater.from(mContext);
View viewOne = inflater.inflate(R.layout.layou_view_one, null);
View viewTwo = inflater.inflate(R.layout.layou_view_two, null);
View viewThree = inflater.inflate(R.layout.layou_view_three, null);
mListView.add(viewOne);
mListView.add(viewOne);
mListView.add(viewThree);
}
private void initView() {
mContext = this;
viewPager = (ViewPager) findViewById(R.id.vp);
}
}
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