点击返回 退出应用

@Override
public void onBackPressed() {
    new AlertDialog.Builder(this).setTitle("确认退出吗？")
            .setIcon(android.R.drawable.ic_dialog_info)
            .setPositiveButton("肯定", new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
                    // 点击“确认”后的操做
                    Intent home = new Intent(Intent.ACTION_MAIN);
                    home.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                    home.addCategory(Intent.CATEGORY_HOME);
                    startActivity(home);
                }
            })
            .setNegativeButton("返回", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    // 点击“返回”后的操做,这里不设置没有任何操做
                }
            }).show();
    // super.onBackPressed();
}

@Override
public void onBackPressed() {
    new AlertDialog.Builder(this).setTitle("确认退出吗？")
            .setIcon(android.R.drawable.ic_dialog_info)
            .setPositiveButton("肯定", new DialogInterface.OnClickListener() {

                @Override
public void onClick(DialogInterface dialog, int which) {
                    // 点击“确认”后的操做
Intent home = new Intent(Intent.ACTION_MAIN);
home.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
home.addCategory(Intent.CATEGORY_HOME);
startActivity(home);
}
            })
            .setNegativeButton("返回", new DialogInterface.OnClickListener() {
                @Override
public void onClick(DialogInterface dialog, int which) {
                    // 点击“返回”后的操做,这里不设置没有任何操做
}
            }).show();
// super.onBackPressed();}