Android Activity 的生命周期(Life Cycle)

这是一个认识Android应用程式生命周期的练习. 通过这个练习知道,原来按下HOME按钮离开应用程式,和按下BACK按钮或调用finish()方法离开应用程式是不相同的.

按下HOME按钮离开应用程式,会顺序调用: OnPause() -> OnStop(). 再次进入应用程式会调用: OnReStart() -> OnStart() -> OnResume(). 

按下BACK按钮或调用finish()方法离开应用程式: OnPause() -> OnStop() -> onDestroy(). 再次进入应用程式会调用: OnCreate() -> OnStart() -> OnResume().

布局代码如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   >
<TextView
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="@string/hello"
   />
<Button
   android:id="@+id/finish"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="exit App by finish()"
   />
</LinearLayout>

后台代码如下：

package com.example.helloworld;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
 
public class MainActivity extends Activity {
   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       
       Button finish = (Button)findViewById(R.id.finish);
       /*finish.setOnClickListener(new Button.OnClickListener()
       {

        public void onClick(View v) {
            // TODO Auto-generated method stub
            
        }
           
       });*/
       finish.setOnClickListener(new Button.OnClickListener(){
 
   public void onClick(View v) {
    // TODO Auto-generated method stub
    finish();
    Toast.makeText(MainActivity.this, "onClick", Toast.LENGTH_LONG);
   }});
       
       Toast.makeText(this, "onCreate", Toast.LENGTH_LONG).show();
       
   }
 
 @Override
 protected void onDestroy() {
  // TODO Auto-generated method stub
  super.onDestroy();
  Toast.makeText(this, "onDestroy", Toast.LENGTH_LONG).show();
 }
 
 @Override
 protected void onPause() {
  // TODO Auto-generated method stub
  super.onPause();
  Toast.makeText(this, "onPause", Toast.LENGTH_LONG).show();
 }
 
 @Override
 protected void onRestart() {
  // TODO Auto-generated method stub
  super.onRestart();
  Toast.makeText(this, "onRestart", Toast.LENGTH_LONG).show();
 }
 
 @Override
 protected void onResume() {
  // TODO Auto-generated method stub
  super.onResume();
  Toast.makeText(this, "onResume", Toast.LENGTH_LONG).show();
 }
 
 @Override
 protected void onStart() {
  // TODO Auto-generated method stub
  super.onStart();
  Toast.makeText(this, "onStart", Toast.LENGTH_LONG).show();
 }
 
 @Override
 protected void onStop() {
  // TODO Auto-generated method stub
  super.onStop();
  Toast.makeText(this, "onStop", Toast.LENGTH_LONG).show();
 }
}

Android Activity的生命周期图如下：