android 之按返回键俩次退出程序

我们使用Handler来实现这个目的   一般也可以使用延时来实现  使用的是工具类DoubleClickExitHelper

java code

import android.app.Activity;
import android.os.Handler;
import android.os.Looper;
import android.view.KeyEvent;
import android.widget.Toast;

public class DoubleClickExitHelper {
	
	private final Activity mActivity;
	
	private boolean isOnKeyBacking;
	private Handler mHandler;
	private Toast mBackToast;
	
	public DoubleClickExitHelper(Activity activity) {
		mActivity = activity;
		mHandler = new Handler(Looper.getMainLooper());
	}
	
	/**
	 * Activity onKeyDown事件
	 * */
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if(keyCode != KeyEvent.KEYCODE_BACK) {
			return false;
		}
		if(isOnKeyBacking) {
			mHandler.removeCallbacks(onBackTimeRunnable);
			if(mBackToast != null){
				mBackToast.cancel();
			}
			mActivity.finish();
			return true;
		} else {
			isOnKeyBacking = true;
			if(mBackToast == null) {
				//mBackToast = Toast.makeText(mActivity, "再按一次返回", 2000);  
			}
			mHandler.postDelayed(onBackTimeRunnable, 2000);
			return true;
		}
	}
	
	private Runnable onBackTimeRunnable = new Runnable() {
		
		@Override
		public void run() {
			isOnKeyBacking = false;
			if(mBackToast != null){
				mBackToast.cancel();
			}
		}
	};
}

在MianActivity里面

        DoubleClickExitHelper doubleClick = new DoubleClickExitHelper(this);  

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {

		if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
			return doubleClick.onKeyDown(keyCode, event);
		}
		return super.onKeyDown(keyCode, event);
	}

实现的效果