Android 期末课堂代码总结
yyt期末_Android课堂总结
计算器的简单实现
题目：运用Android Studio编写一个简单计算器APP
- 对按钮功能的监听
/**
* 数字按钮监听器
**/
class clickNum implements OnClickListener {
public void onClick(View v) {
Button num = (Button) v; //获取用户点击的按钮对象
String clickNum = num.getText().toString(); //获取用户点击的数字
progress = showRst.getText().toString(); //获取结果的值并赋值给progress
if(v == btn0){
//按0
progress = dealRes(progress,clickNum);
}else {
//按1-9
progress = dealRes(progress,clickNum);
}
showRst.setText(progress);
}
}
/**
* 功能按钮监听器
*
* 可以加“.”的情况
* \\d+ \\d+\+|-|/|\*\\d+ \\d+\\.\\d+\+|-|/|\*\\d+
*
*/
class clickOther implements OnClickListener {
public void onClick(View v) {
Button num = (Button) v;
String reg = "^(\\d+)|^(\\d+\\+|-|/|\\*\\d+)|^(\\d+\\.\\d+\\+|-|/|\\*\\d+)";
String symbol = num.getText().toString(); //获取用户点击的符号
progress = showRst.getText().toString(); //获取结果的值并赋值给progress
//按清除按钮
if(v == clear){
progress = "0";
currentSymbol = "";
//按等号按钮
} else if(v == btnEq) {
String []arr = progress.split("\\+|-|/|\\*");
if(progress.split("\\+|-|/|\\*").length != 1) {
progress = splitStr(progress,currentSymbol);
}
//按“.”按钮
} else if ( v == btnDot) {
//如果不符合可以加“.”的情况，则不变，否则加上“.”
progress = !Pattern.matches(reg,progress) ? progress : dealRes(progress,symbol);
//按加减乘除按钮
} else {
//如果式子中存在“+*/”，进行运算；如果存在“-”且不是首位，进行运算
Boolean a = progress.indexOf('+') != -1 || progress.indexOf('*') != -1 || progress.indexOf('/') != -1;
Boolean b = progress.indexOf('-') != -1;
Boolean c = progress.lastIndexOf('-') != 0;
if (a) {
progress = splitStr(progress,currentSymbol);
currentSymbol = num.getText().toString();
progress = progress + currentSymbol;
} else if (b && c) {
progress = splitStr(progress,currentSymbol);
currentSymbol = num.getText().toString();
progress = progress + currentSymbol;
} else {
currentSymbol = num.getText().toString();
progress = progress + currentSymbol;
}
}
showRst.setText(progress);
}
}
- 运算逻辑处理
/**
* 分割字符串，进行计算。并返回计算结果
* 两个参数：完整式子，运算符号
*/
public String splitStr (String str , String calSymbol) {
String []strArray = new String[20];
strArray = str.split("\\+|-|/|\\*"); //使用+-*/对式子进行分割
Double res = 0.0;
switch (calSymbol) {
//根据运算符号选取操作
case "+" : {
if (strArray.length > 2) res = (- Double.parseDouble(strArray[1])) + Double.parseDouble(strArray[2]);
else res = Double.parseDouble(strArray[0]) + Double.parseDouble(strArray[1]);
currentSymbol = "";
break;
}
case "-" : {
if (strArray.length > 2) res = (- Double.parseDouble(strArray[1])) - Double.parseDouble(strArray[2]);
else res = str.indexOf('-') == 0 ? Double.parseDouble(str) : Double.parseDouble(strArray[0]) - Double.parseDouble(strArray[1]);
currentSymbol = "";
break;
}
case "*" : {
if (strArray.length > 2) res = (- Double.parseDouble(strArray[1])) * Double.parseDouble(strArray[2]);
else res = Double.parseDouble(strArray[0]) * Double.parseDouble(strArray[1]);
currentSymbol = "";
break;
}
case "/" : {
if (strArray.length > 2) res = (- Double.parseDouble(strArray[1])) / Double.parseDouble(strArray[2]);
else res = Double.parseDouble(strArray[0]) / Double.parseDouble(strArray[1]);
currentSymbol = "";
break;
}
}
return String.valueOf(res);
}
/**
* 判断字符串组成，并返回结果
*/
public String dealRes (String str,String clickSymbol){
String reValue = "";
//如果字符串长度为0，直接返回点击的字符
if (str.length() == 0) {
reValue = clickSymbol;
//如果字符串长度为为1，且等于0，且字符不为“.”，则返回点击的字符
} else if(str.length() == 1 && Integer.parseInt(str) == 0 && clickSymbol != btnDot.getText().toString()) {
reValue = clickSymbol ;
//其他情况，直接拼接点击的字符字符
} else {
reValue = str + clickSymbol;
}
return reValue;
}
Intent的运用
题目：MainActivity.java和Main2Activity.java。MainActivity中输入姓名和密码，点击登录能够传递到对应的 Activity，并显示到其 TextView 组件上。name 是姓名文本编辑框变量，passwd 是密码文本编辑框变量，login 是登录按钮变量。
- MainActivity.java 源代码如下：
public class MainActivity extends AppCompatActivity {
EditText name,passwd;
Button login,cancel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
name=findViewById(R.id.editText3);
passwd=findViewById(R.id.editText4);
login=findViewById(R.id.button);
cancel=findViewById(R.id.button2);
login.setOnClickListener (new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent=new Intent(MainActivity.this,Main2Activity.class)
intent.putExtra("userName", name.getText().tostring().trim() );
intent.putExtra("password", password.getText().tostring().trim() );
start Activity(intent);
}
});
}
}
- Main2Activity.java 源代码如下：
public class Main2Activity extends AppCompatActivity {
TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
textView=findViewById(R.id.textView);
Intent intent = getIntent() ;
String userName = intent.getStringExtra(“userName”) ;
String password = intent.getStringExtra(“password”) ;
textView.setText ("用户名；"+userName+"\n"+"密码："+password);
}
}
ListView运用
题目：利用 ListView 组件设计如下图所示的界面效果，点击 ListView 中的某一项时，会将这一项的文字信息显示在 Toast 窗口中。
public class MainActivity extends AppCompatActivity {
ListView listView;
String []title=new String[]{
"数据","分层","位置","视频","通知","购物车","信息","点赞"};
int []image=new int[]{
R.drawable.img01,R.drawable.img02,R.drawable.img03,
R.drawable.img04,R.drawable.img05,R.drawable.img06,
R.drawable.img07,R.drawable.img08};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = view.findViewById(R.id.listView);
List<Map<String,Object>> list=new ArrayList<>();
for(int i=0;i<title.length;i++) {
Map<String,Object> map=new HashMap<>();
map.put("title",title[i]);
map.put("image",image[i]);
list.add(map);
}
SimpleAdapter adapter=newSimpleAdapter(MainActivity.this, list ,
R.layout.item,
new String[]{
"title","image"},
new int[]{
R.id.textView,R.id.imageView});
listView.setAdapter(adapter);
listView. listView.setAdapter(adapter); (newAdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View
view, int position, long id) {
Toast.makeText(MainActivity.this, listView.setAdapter(adapter),Toast.LENGTH_SHORT).show();
}
});
}
}
广播消息Broadcast
题目：MainActivity.java，文本框中输入信息，点击“发送广播”按钮，广播接收器(MyBroadcastReceiver.java)的处理方式是将接收到的信息显示在 Toast 窗口中,完成下面的程序填空。
public class MainActivity extends AppCompatActivity{
private EditText entryText ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
entryText = (EditText)findViewById(R.id.entry);
}
public void send(View view){
Intent intent = new Intent(MainActivity.this,MyBroadcastReceiver.class);
intent.putExtra("message",entryText.getText().toSting().trim());
sentBroadcast(intent);
}
}
public class MyBroadcastReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context, Intent intent) {
String msg = intent.getStringExtra(“message”);
Toast.makeText(context, msg, Toast.LENGTH_SHORT).show();
}
}
数据库SQLite
题目：现在需要管理的学生信息如下：学号、姓名、身份证号、性别、家庭住址、监护人、监护人电话。要求用 SQLite 数据库存储，并定义对数据库中的数据表进行增删改查功能的Student_Database 类，学生实体类 Student.java 已经提供。
public class Student{
private int id;
private String username;
private String personalid;
private String sex;
private String address;
private String parent;
private String parentphone;
public Student (int id,String username,String personal_id,String sex,String address,String parent,String parentphone){
this.id=id;
this.username=username;
this.personalid=personal_id;
this.sex=sex;
this.address=address;
this.parent=parent;
this.parentphone=parentphone;
}
//关于属性的 set 和 get 函数省略
// ……
}
public final class Student_Database extends SQLiteOpenHelper{
static int counter=20180001;
public Student_Database(Context context){
super(context,"student-db.db",null,3);
}
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
try {
db.execSQL("drop table if exists "+"student");
onCreate(db);
}
catch (SQLException e) {
e.printStackTrace();
}
}
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
String sql="create table student(id integer primary key autoincrement," +
"username text not null," +
"personalid text not null," +
"sex text not null," +
"address text not null," +
"parent text not null," +
"parentphone text not null)";
sqLiteDatabase.execSQL(sql)
}
public void adddata(SQLiteDatabase sqLiteDatabase,String name,String personalid,String sex,String address,String parent,String parentphone){
counter++;
ContentValues values=new ContentValues();
values.put("id",counter);
values.put("username",name);
values.put("personalid",personalid);
values.put("sex",sex);
values.put("address",address);
values.put("parent",parent);
values.put("parentphone",parentphone);
sqLiteDatabase.insert("user",null,values);
sqLiteDatabase.close();
}
public void delete(SQLiteDatabase sqLiteDatabase,int id){
sqLiteDatabase.delete("user","id=?", new String[]{
id+""});
sqLiteDatabase.close();
}
public void update(SQLiteDatabase sqLiteDatabase,int id,String name,String personalid,String sex,String address,String parent,String parentphone){
ContentValues values = new ContentValues();
values.put("username",name);
values.put("sex",sex);
values.put("personalid",personalid);
values.put("address",address);
values.put("parent",parent);
values.put("parentphone",parentphone);
sqLiteDatabase.update( table”student” ,values,"id=?",new String[]{
id+""});
sqLiteDatabase.close();
}
public List<Student> queryData(SQLiteDatabase sqLiteDatabase){
Cursor cursor=sqLiteDatabase.query("student",null,null,null,null,null,"id ASC");
List< Student> list= new ArrayList< Student>();
while(cursor.moveToNext()){
int id=cursor.getInt(cursor.getColumnIndex("id"));
String username=cursor.getString(1);
String personalid=cursor.getString(2);
String sex=cursor.getString(3);
String address=cursor.getString(4);
String parent=cursor.getString(5);
String parentphone=cursor.getString(6);
list.add(new Student(id,username,personalid,sex,address,parent,parentphone));
}
cursor.close();
sqLiteDatabase.close();
return list;
}
}