步骤一、实现onKeyDown方法(核心代码如下)
package com.veryedu.back; import android.os.Bundle; import android.os.Handler; import android.app.Activity; import android.view.KeyEvent; import android.view.Menu; import android.widget.Toast; public class MainActivity extends Activity { boolean flag=false; @Override public boolean onKeyDown(int keyCode, KeyEvent event) { // TODO Auto-generated method stub if(keyCode==KeyEvent.KEYCODE_BACK){ if(flag){ return super.onKeyDown(keyCode, event); }else{ flag=true; Toast.makeText(MainActivity.this, "三秒之内再次按下回退键推出程序!!!", Toast.LENGTH_LONG).show(); Handler handler=new Handler(); handler.postDelayed(new Runnable() { @Override public void run() { // TODO Auto-generated method stub } }, 3000); } } return super.onKeyDown(keyCode, event); } @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } }
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