[转]Android应用中返回键的监听及处理

 

 

用户在点击手机的返回按钮时，默认是推出当前的activty，但是有时用户不小心按到返回，所以需要给用户一个提示，这就需要重写onkeydown事件，实现的效果如下：

 

标签：    Android SDK    

 

        

       

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@Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.main);     }     protected void dialog() {         AlertDialog.Builder builder = new Builder(HanderTestActivty.this);         builder.setMessage("确定要退出吗?");         builder.setTitle("提示");         builder.setPositiveButton("确认",                 new android.content.DialogInterface.OnClickListener() {                     @Override                     public void onClick(DialogInterface dialog, int which) {                         dialog.dismiss();                         HanderTestActivty.this.finish();                     }                 });         builder.setNegativeButton("取消",                 new android.content.DialogInterface.OnClickListener() {                     @Override                     public void onClick(DialogInterface dialog, int which) {                         dialog.dismiss();                     }                 });         builder.create().show();     }     @Override     public boolean onKeyDown(int keyCode, KeyEvent event) {         if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {             dialog();             return false;         }         return false;     }

 

 

 

 

 

 

 

 

 

 

 

MainActivity如下:

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package com.testnbackpressed;  import android.os.Bundle;  import android.view.KeyEvent;  import android.app.Activity;  /**  * Demo描述:  * 处理Back键按下事件  *   * 注意事项:  * 以下两种方法勿一起使用  */  public class MainActivity extends Activity {          @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.main);      }      /**      * 监听Back键按下事件,方法1:      * 注意:      * super.onBackPressed()会自动调用finish()方法,关闭      * 当前Activity.      * 若要屏蔽Back键盘,注释该行代码即可      */      @Override      public void onBackPressed() {          super.onBackPressed();          System.out.println("按下了back键   onBackPressed()");             }                     /**     * 监听Back键按下事件,方法2:     * 注意:     * 返回值表示:是否能完全处理该事件     * 在此处返回false,所以会继续传播该事件.     * 在具体项目中此处的返回值视情况而定.     */      @Override      public boolean onKeyDown(int keyCode, KeyEvent event) {          if ((keyCode == KeyEvent.KEYCODE_BACK)) {               System.out.println("按下了back键   onKeyDown()");                return false;          }else {              return super.onKeyDown(keyCode, event);          }                  }              @Override      protected void onDestroy() {          super.onDestroy();          System.out.println("执行 onDestroy()");      }         }

 

main.xml如下:

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<RelativeLayout       xmlns:android="http://schemas.android.com/apk/res/android"      xmlns:tools="http://schemas.android.com/tools"      android:layout_width="match_parent"      android:layout_height="match_parent"      >          <TextView          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:text="对于Back键的两种处理方法"          android:layout_centerInParent="true"          android:textSize="20sp"     />      </RelativeLayout>