双击返回键返回

    package com.anjoyo.test;

    import android.app.Activity;
    import android.os.Bundle;
    import android.view.KeyEvent;
    import android.widget.Toast;

    public class TestActivity extends Activity {
            private long mExitTime;

            public void onCreate(Bundle savedInstanceState) {
                    super.onCreate(savedInstanceState);
                    setContentView(R.layout.main);

            }
            
            public boolean onKeyDown(int keyCode, KeyEvent event) {
                    if (keyCode == KeyEvent.KEYCODE_BACK) {
                            if ((System.currentTimeMillis() - mExitTime) > 2000) {
                                    Object mHelperUtils;
                                    Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
                                    mExitTime = System.currentTimeMillis();

                            } else {
                                    finish();
                            }
                            return true;
                    }
                    return super.onKeyDown(keyCode, event);
            }
    }

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