扣丁学堂笔记第08天Activity组件
1.Activity概述
2.状态与生命周期（三大状态与七大方法）
状态
生命周期
onCreate()：创建Activity第一个被调用的方法，用于加载布局，初始化UI组件，注册事件；
onStart()：在onCreate()之后被调用，用于显示界面，但界面与用户还不能进行交互；
onResume()：在onStart()之后被调用，该方法执行完成后，用户与界面可以进行交互，当前Activity进入resumed状态（运行状态）；
当一个paused状态的Activity重新返回时，会再次调用该方法，让Activity进入运行状态；
onPause()：当其他Activity（透明或窗口模式）进入时，该方法会被调用，让当前Activity进入paused状态（暂停状态）；
当前Activity还可见但不可交互，如果其他更高级别的App需要内存时，当前Activity可能会被销毁（killed）；
当前Activity被返回时，会调用onResume()方法；
onStop()：当其他Activity完全覆盖该Activity时，会被调用，当前Activity进入stopped状态（停止状态）；
不可见，如果其他更高级别的APP需要内存时，当前Activity可能会被销毁（killed）；
当前Activity被返回时，会调用onRestart()方法；
onRestart()：当一个stopped的Activity被返回时时调用，之后再调用onResume()进入resumed状态（运行状态）；
onDestroy()：当前Activity被销毁时调用，通常用来释放资源，当前Activity killed；
3.传递简单数据
MainActivity
package com.example.activitytest;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
public class MainActivity extends Activity {
private EditText editText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText = (EditText) findViewById(R.id.editText1);
}
public void sendClick(View v){
Intent intent = new Intent(this,Activity2.class);
String info = editText.getText().toString();
// 传递数据
// 方式一：通过Bundle封装数据，再把数据放入intent，Activity2得到数据是逆向的
// Bundle data = new Bundle();
// data.putString("info", info);
// intent.putExtra("data", data);
// 方式二：直接调用
intent.putExtra("info", info);
startActivity(intent);
}
}
Activity2
package com.example.activitytest;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
public class Activity2 extends Activity{
private TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_2);
textView = (TextView) findViewById(R.id.tv_2);
Intent intent = getIntent();
// Bundle data = getIntent().getBundleExtra("data");
// String info = data.getString("info");
String info = intent.getStringExtra("info");
textView.setText(info);
}
}
4.传递自定义对象数据
通过自定义类实现Serializable接口和Parcelable接口来传递自定义对象的数据
Cat.java
package com.example.activitytest;
import java.io.Serializable;
public class Cat implements Serializable{
String name;
int age;
String type;
@Override
public String toString() {
return "Cat [name=" + name + ", age=" + age + ", type=" + type + "]";
}
}
Dog.java
package com.example.activitytest;
import android.os.Parcel;
import android.os.Parcelable;
public class Dog implements Parcelable{
String name;
int age;
String type;
@Override
public int describeContents() {
// TODO Auto-generated method stub
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
// TODO Auto-generated method stub
dest.writeString(name);
dest.writeInt(age);
dest.writeString(type);
}
@Override
public String toString() {
return "Dog [name=" + name + ", age=" + age + ", type=" + type + "]";
}
public static final Parcelable.Creator<Dog> CREATOR
= new Parcelable.Creator<Dog>() {
public Dog createFromParcel(Parcel in) {
Dog dog = new Dog();
dog.name = in.readString();
dog.age = in.readInt();
dog.type = in.readString();
return dog;
}
public Dog[] newArray(int size) {
return new Dog[size];
}
};
}
MainActivity.java
package com.example.activitytest;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
public class MainActivity extends Activity {
private EditText editText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText = (EditText) findViewById(R.id.editText1);
}
public void sendClick(View v) {
Intent intent = new Intent(this, Activity2.class);
String info = editText.getText().toString();
// 传递数据
// 方式一：通过Bundle封装数据，再把数据放入intent，Activity2得到数据是逆向的
// Bundle data = new Bundle();
// data.putString("info", info);
// intent.putExtra("data", data);
// 方式二：直接调用
intent.putExtra("info", info);
startActivity(intent);
}
public void sendobj1Click(View v) {
Cat cat = new Cat();
cat.name = "皮卡丘";
cat.age = 2;
cat.type = "美短";
Intent intent = new Intent(this, Activity2.class);
intent.putExtra("cat", cat);
startActivity(intent);
}
public void sendobj2Click(View v) {
Dog dog = new Dog();
dog.name = "汪汪";
dog.age = 1;
dog.type = "萨摩耶";
Intent intent = new Intent(this, Activity2.class);
intent.putExtra("dog", dog);
startActivity(intent);
}
}
Activity2.java
package com.example.activitytest;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
public class Activity2 extends Activity{
private TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_2);
textView = (TextView) findViewById(R.id.tv_2);
Intent intent = getIntent();
// Bundle data = getIntent().getBundleExtra("data");
// String info = data.getString("info");
// String info = intent.getStringExtra("info");
// textView.setText(info);
// Cat cat = (Cat) intent.getSerializableExtra("cat");
// textView.setText(cat.toString());
Dog dog = intent.getParcelableExtra("dog");
textView.setText(dog.toString());
}
}
5.处理返回结果
调用startActivity()方法，并且重写onActivityResult()方法：接收三个参数：requestCode（在starttActivityResult中设置）、resultOK（在点击事件设置）、data；
点击事件onItemClick:先根据position得到数据，定义为字符串类型，在调用intent的putExtra方法放入数据，再调用setResult方法，然后finish()；
具体onActivityResult()代码：使用if语句，如果requestCode和resultCode都满足要求，就getStringExtra()，然后再editText中setText()；
要实现点击按钮模拟拨号的界面，调用intent的setAction()传入Intent.ACTION_CALL,再调用setData方法传入Uri.parse("tel:"+number);
最后别忘了在清单文件中加入CALL_PHONE的权限
本节踩过好多坑啊！！！代码量还是不够，还是经验不足啊！！！
1.RESULT_O我居然自己赋值了，要哭！
2.自己创建的Activity忘记在清单文件中注册了！
3.实现接口类的监听事件忘记在onCreate里注册了！
4.getIntent()方法乱用啊！得是new Intent()！
5.忘记在清单文件里添加打电话的用户权限了！
MainActivity
package com.example.callphonetest;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
public class MainActivity extends Activity {
private static final int REQUEST_CODE = 0x1;
private EditText editText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText = (EditText) findViewById(R.id.editText1);
}
public void selectClick(View v){
Intent intent = new Intent(this,PhoneNumberActivity.class);
startActivityForResult(intent, REQUEST_CODE);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// TODO Auto-generated method stub
super.onActivityResult(requestCode, resultCode, data);
if(requestCode==REQUEST_CODE&&resultCode==RESULT_OK){
String number = data.getStringExtra("number");
editText.setText(number);
}
}
public void callClick(View v){
String number = editText.getText().toString();
Intent intent = new Intent();//这里写getIntent()_就不行了，哎，还是太嫩，很多都不懂
intent.setAction(Intent.ACTION_CALL);
intent.setData(Uri.parse("tel:"+number));
startActivity(intent);
}
}
PhoneNumberActivity
package com.example.callphonetest;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class PhoneNumberActivity extends Activity implements OnItemClickListener{
private ListView listView;
private String[] numbers ={"131****2160","10010","1001011","159****4296"};
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.number_layout);
listView = (ListView) findViewById(R.id.listView);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,android.R.id.text1,numbers);
listView.setAdapter(adapter);
listView.setOnItemClickListener(this);
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// TODO Auto-generated method stub
String number = numbers[position];
Intent intent = new Intent(this,MainActivity.class);
intent.putExtra("number", number);
setResult(RESULT_OK, intent);//在RESULT_OK这里醉了，收REQUEST_CODE影响，惯性思维也给它赋了一个值，我死去的时间啊！！！
finish();
}
}
6.屏幕方向与显示方向
7.屏幕方向旋转
屏幕旋转后，默认会重新创建一个Activity，为了保存之前Activity状态，可以重写onSaveInstanceState()方法来保存相关数据，然后在onCreate()方法里还原数据
8.SharedPreferences
Activity通过SharedPreferences保存数据
MainActivity
package com.example.sharedpreferencestest;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.text.TextUtils;
import android.widget.EditText;
public class MainActivity extends Activity {
private EditText editText;
private SharedPreferences sp;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText = (EditText) findViewById(R.id.editText1);
sp = getSharedPreferences("msg", Context.MODE_PRIVATE);
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
editText.setText(sp.getString("msg", ""));
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
String msg = editText.getText().toString();
if(TextUtils.isEmpty(msg)){
return;
}
SharedPreferences.Editor editor = sp.edit();
editor.putString("msg", msg);
editor.commit();
}
}