Android Toast 提示按两次返回键退出

 1 public class MainActivity extends Activity {
 2 
 3     @Override
 4     protected void onCreate(Bundle savedInstanceState) {
 5         super.onCreate(savedInstanceState);
 6         setContentView(R.layout.activity_main);
 7 
 8     }
 9 
10     long startTime;
11 
12     @Override
13     public void onBackPressed() {
14         if (System.currentTimeMillis() - startTime < 2000) {
15             super.onBackPressed();
16         } else {
17             startTime = System.currentTimeMillis();
18 
19             Toast toast = new Toast(this);
20 
21             LinearLayout layout = new LinearLayout(this);
22             layout.setOrientation(LinearLayout.VERTICAL);
23             layout.setBackgroundColor(Color.YELLOW);
24             
25             TextView tv1 = new TextView(this);
26             tv1.setText("提示");
27             tv1.setGravity(Gravity.CENTER);
28             
29             TextView tv2 = new TextView(this);
30             tv2.setText("再按一次Back键退出");
31             tv2.setGravity(Gravity.CENTER);
32             
33             layout.addView(tv1);
34             layout.addView(tv2);
35 
36             toast.setView(layout);
37             toast.setGravity(Gravity.CENTER_VERTICAL | Gravity.FILL_HORIZONTAL, 0, -200);
38             toast.setDuration(Toast.LENGTH_SHORT);
39             toast.show();
40 
41         }
42 
43     }
44 
45 }