KeyEvent事件-再按一次退出 常见对话框退出

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
        new AlertDialog.Builder(KeyEventTestActivity.this)
                .setMessage("要退出吗")
                .setNegativeButton("退出", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        finish();
                    }
                })
                .setPositiveButton("再看看",null)
                .show();
        return true;/**不会再退出了*/
    }

    return super.onKeyDown(keyCode, event);
}

有多个页面时 需要用intent强制退出

@Override
public void onBackPressed() {
    if ((System.currentTimeMillis() - mExitTime) > 2000) {
        Toast.makeText(this, "再次点击返回键退出界面",
                Toast.LENGTH_SHORT).show();
        mExitTime = System.currentTimeMillis();
    } else {
        goHome(this);
    }
}

/**
 * 回到桌面
 *
 * @param context 上下文
 */
public static void goHome(Context context) {
    try {
        Intent startMain = new Intent(Intent.ACTION_MAIN);
        startMain.addCategory(Intent.CATEGORY_HOME);
        startMain.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        context.startActivity(startMain);
    } catch (Exception e) {
        e.printStackTrace();
    }
}