"Go" Android implementation click two times back key to exit

In the Android application is we often have to judge the user to the return key operation, generally to prevent misoperation is the user repeatedly press two times the return button when the user is prompted to quit the application.

The basic principle of the first implementation is that when the back key is pressed, it is captured by onkeydown and the back key is determined, then the exit method is executed.
In the Exit method, the value of Isexit is first judged, if False, it is set to true, and a prompt pops up, and a message is issued after 2000 milliseconds (2 seconds), and the value is reverted to false in handler. If the back key is pressed again within 2 seconds of the sending message interval, the exit method is executed again, and the exit method is executed when the value of Isexit is true.

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Package com.Gaolei.Exitdemo;ImportAndroid.app.Activity;ImportAndroid.os.Bundle;ImportAndroid.os.Handler;ImportAndroid.os.Message;ImportAndroid.view.KeyEvent;ImportAndroid.widget.Toast;PublicClassMainactivityExtends Activity{Define a variable to identify whether to exitPrivateStaticBoolean isexit=False; Handler Mhandler=New Handler(){@OverridePublicvoidHandlemessage(Message msg){Super.Handlemessage(msg); Isexit=False;}};@OverrideProtectedvoidOnCreate(Bundle savedinstancestate){Super.OnCreate(savedinstancestate); Setcontentview(R.Layout.Activity_main);}@OverridePublicBooleanOnKeyDown(int KeyCode, KeyEvent Event){If(KeyCode= = KeyEvent.Keycode_back){Exit();ReturnFalse;}ReturnSuper.OnKeyDown(KeyCode, event);}PrivatevoidExit(){If(!isexit){Isexit=True; Toast.Maketext(Getapplicationcontext(),"Press one more time to exit the program", Toast.Length_short).show (); . sendemptymessagedelayed 02000} else {finish(); System. Exit (0} }

The second implementation method, by recording the key time to calculate the difference in timing:

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Package com.Gaolei.Exitdemo;ImportAndroid.app.Activity;ImportAndroid.os.Bundle;ImportAndroid.view.KeyEvent;ImportAndroid.widget.Toast;PublicClassMainactivityExtends Activity{PrivateLong Exittime=0;@OverrideProtectedvoidOnCreate(Bundle savedinstancestate){Super.OnCreate(savedinstancestate); Setcontentview(R.Layout.Activity_main);}@OverridePublicBooleanOnKeyDown(int KeyCode, KeyEvent Event){If(KeyCode= = KeyEvent.Keycode_back){Exit();ReturnFalse;}ReturnSuper.OnKeyDown(KeyCode, event);}PublicvoidExit(){If(System.Currenttimemillis()-Exittime)>2000){Toast.Maketext(Getapplicationcontext(), Toast.< Span style= "color: #7d9029;" >length_short). show () exittime = System. Currenttimemillis (); else (); System. Exit (0} }

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"Go" Android implementation click two times back key to exit