监听返回键并退出所有Activity示例

下面给出3个简单的Activity，并在它们之间跳转，如果想点击某个Activity的返回键时就退出所有Activity，就只需监听该Activity的返回键即可。所有Activity都存放在一个集合里面，退出应用时，只需遍历该集合并逐一finish掉。代码如下：

MyAppalication：存放所有activity，提供添加activity和退出所有activity的方法

package com.home.exitapp;

import java.util.ArrayList;

import android.app.Activity;
import android.app.Application;

public class MyAppalication extends Application {
	// 存放activity的集合
	private ArrayList<Activity> list = new ArrayList<Activity>();
	private static MyAppalication instance;

	public MyAppalication() {
	}

	/**
	 * 利用单例模式获取MyAppalication实例
	 * 
	 * @return
	 */
	public static MyAppalication getInstance() {
		if (null == instance) {
			instance = new MyAppalication();
		}
		return instance;
	}

	/**
	 * 添加activity到list集合
	 * 
	 * @param activity
	 */
	public void addActivity(Activity activity) {
		list.add(activity);

	}

	/**
	 * 退出集合所有的activity
	 */
	public void exit() {
		try {
			for (Activity activity : list) {
				activity.finish();
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			System.exit(0);
		}
	}

	@Override
	public void onLowMemory() {
		super.onLowMemory();
		System.gc();
	}
}

BaseActivity：抽象出添加activity的方法

package com.home.exitapp;

import android.app.Activity;
import android.os.Bundle;

public class BaseActivity extends Activity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		MyAppalication.getInstance().addActivity(BaseActivity.this);
	}

}

MyActivity1：

package com.home.exitapp;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MyActivity1 extends BaseActivity {
	private Button btn_1_2;
	private Button btn_1_3;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main1);
		// MyAppalication.getInstance().addActivity(MyActivity1.this);
		btn_1_2 = (Button) findViewById(R.id.main1_btn_1_2);
		btn_1_3 = (Button) findViewById(R.id.main1_btn_1_3);
		btn_1_2.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				Intent intent = new Intent(MyActivity1.this, MyActivity2.class);
				startActivity(intent);
			}
		});

		btn_1_3.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				Intent intent = new Intent(MyActivity1.this, MyActivity3.class);
				startActivity(intent);
			}
		});
	}

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
			// return true;//返回真表示返回键被屏蔽掉
			creatDialog();// 创建弹出的Dialog
		}
		return super.onKeyDown(keyCode, event);
	}

	/**
	 * 弹出提示退出对话框
	 */
	private void creatDialog() {
		new AlertDialog.Builder(this)
				.setMessage("确定退出app?")
				.setPositiveButton("YES",
						new DialogInterface.OnClickListener() {

							@Override
							public void onClick(DialogInterface dialog,
									int which) {
								MyAppalication.getInstance().exit();
							}
						})
				.setNegativeButton("NO", new DialogInterface.OnClickListener() {

					@Override
					public void onClick(DialogInterface dialog, int which) {
						dialog.dismiss();
					}
				}).show();
	}
}

MyActivity2：

package com.home.exitapp;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MyActivity2 extends BaseActivity {
	private Button btn_2_1;
	private Button btn_2_3;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main2);
		btn_2_1 = (Button) findViewById(R.id.main2_btn_2_1);
		btn_2_3 = (Button) findViewById(R.id.main2_btn_2_3);
		btn_2_1.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				Intent intent = new Intent(MyActivity2.this, MyActivity1.class);
				startActivity(intent);
			}
		});

		btn_2_3.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				Intent intent = new Intent(MyActivity2.this, MyActivity3.class);
				startActivity(intent);
			}
		});
	}

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
			// return true;//返回真表示返回键被屏蔽掉
			creatDialog();// 创建弹出的Dialog
		}
		return super.onKeyDown(keyCode, event);
	}

	/**
	 * 弹出提示退出对话框
	 */
	private void creatDialog() {
		new AlertDialog.Builder(this)
				.setMessage("确定退出app?")
				.setPositiveButton("YES",
						new DialogInterface.OnClickListener() {

							@Override
							public void onClick(DialogInterface dialog,
									int which) {
								MyAppalication.getInstance().exit();
							}
						})
				.setNegativeButton("NO", new DialogInterface.OnClickListener() {

					@Override
					public void onClick(DialogInterface dialog, int which) {
						dialog.dismiss();
					}
				}).show();
	}
}

MyActivity3：

package com.home.exitapp;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MyActivity3 extends BaseActivity {
	private Button btn_3_2;
	private Button btn_3_1;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main3);
		btn_3_2 = (Button) findViewById(R.id.main3_btn_3_2);
		btn_3_1 = (Button) findViewById(R.id.main3_btn_3_1);
		btn_3_2.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				Intent intent = new Intent(MyActivity3.this, MyActivity2.class);
				startActivity(intent);
			}
		});

		btn_3_1.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				Intent intent = new Intent(MyActivity3.this, MyActivity1.class);
				startActivity(intent);
			}
		});
	}

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
			// return true;//返回真表示返回键被屏蔽掉
			creatDialog();// 创建弹出的Dialog
		}
		return super.onKeyDown(keyCode, event);
	}

	/**
	 * 弹出提示退出对话框
	 */
	private void creatDialog() {
		new AlertDialog.Builder(this)
				.setMessage("确定退出app?")
				.setPositiveButton("YES",
						new DialogInterface.OnClickListener() {

							@Override
							public void onClick(DialogInterface dialog,
									int which) {
								MyAppalication.getInstance().exit();
							}
						})
				.setNegativeButton("NO", new DialogInterface.OnClickListener() {

					@Override
					public void onClick(DialogInterface dialog, int which) {
						dialog.dismiss();
					}
				}).show();
	}
}

main1.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="I am the first activity"
        android:textSize="25sp" />

    <Button
        android:id="@+id/main1_btn_1_2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="跳到2" />

    <Button
        android:id="@+id/main1_btn_1_3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="跳到3" />

</LinearLayout>

main2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#f000f0"
    android:orientation="vertical" >

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="I am the second activity"
        android:textSize="25sp" />

    <Button
        android:id="@+id/main2_btn_2_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="跳到1" />

    <Button
        android:id="@+id/main2_btn_2_3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="跳到3" />

</LinearLayout>

main3.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#00f0ff"
    android:orientation="vertical" >

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="I am the third activity"
        android:textSize="25sp" />

    <Button
        android:id="@+id/main3_btn_3_2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="跳到2" />

    <Button
        android:id="@+id/main3_btn_3_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="跳到1" />

</LinearLayout>