再点一次退出最简单逻辑

<pre name="code" class="java">private int firstTime=0;
public void onBackPressed() {  
        if ((System.currentTimeMillis() - firstTime) > 2000) {  
            Toast.makeText(MainActivity.this,"再点一次退出",0).show();  
            firstTime = System.currentTimeMillis();  
        } else {  
            finish();  
        }  
    }