Button按钮实现返回键功能

retu.setOnClickListener(new View.OnClickListener() {    @Override    public void onClick(View v) {        new Thread() {            public void run() {                try {                    Instrumentation instrument = new Instrumentation();                    instrument.sendKeyDownUpSync(KeyEvent.KEYCODE_BACK);
                } catch (Exception e) {
                }            }        }.start();    }});