在作安卓應用是咱們常常要判斷用戶對返回鍵的操做,通常爲了防止誤操做都是在用戶連續按下兩次返回鍵的時候提示用戶是否退出應用程序。方法不少種,這裏經過記錄按鍵時間計算時間差實現: android
import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.widget.Toast; app
public class MainActivity extends Activity { ide
private long exitTime = 0; get
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
} it
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
exit();
return false;
}
return super.onKeyDown(keyCode, event);
} io
public void exit() {
if ((System.currentTimeMillis() - exitTime) > 2000) {
Toast.makeText(getApplicationContext(), "再按一次退出程序",
Toast.LENGTH_SHORT).show();
exitTime = System.currentTimeMillis();
} else {
finish();
System.exit(0);
}
} event
} ast