android - 根据 Message 在 handleMessage 中动态更改 onClickListener

Question

我有一个带有 Android.os.Handler 的 Activity ，用于与 openGL 线程通信。我想从 opengl 线程获取消息并根据消息数据在 Activity 中绘制一些 GUI，所以我这样做:

Handler handle = new Handler(new Handler.Callback(){
        public boolean handleMessage(Message msg){
            // update  GUI like
            TextView v1 = (TextView) GamescreenActivity .this.findViewById(R.id.mytextview)
            // then what I actually would like to do but it does not work:
            Button b = (Button) GamescreenActivity.this.findViewById(R.id.mybutton);
            b.setOnClickListener(null);
            if (msg.what == MY_OWN_CONSTANT) { 
                b.setOnClickListener(getOnClickDoSomething(msg));
            }
        }
View.OnClickListener getOnClickDoSomething(final Message msg)  {
    return new View.OnClickListener() {
        public void onClick(View v) {
            makeDialog(msg);
        }
    };
}
private void makeDialog(Message msg) {      
    AlertDialog.Builder builder = new AlertDialog.Builder(GamescreenActivity.this);
    builder.setMessage("yo")
    .setTitle(""+ msg.what);
    AlertDialog dialog = builder.create();
    dialog.show();
}

我希望很清楚我要实现的目标。我现在得到的是 makeDialog 方法中的 msg 几乎一直都是 null。

Answer 1

What I get by now is msg being null in the makeDialog methode almost all the time.

我相信发生这种情况时 Message 已经被回收了。让我们创建一个 msg 的本地副本并稍微修改您的代码以使其更高效。首先新建一个字段变量:

Message message;

接下来更改您的 if-else block :

if (msg.what == MY_OWN_CONSTANT) { 
    message = Message.obtain(msg);
    b.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            AlertDialog.Builder builder = new AlertDialog.Builder(GamescreenActivity.this);
            builder.setMessage("yo")
                    .setTitle(""+ message.what)
                    .show();
            message.recycle(); // Recycle our message when we're done
        }
    });
}
else {
    b.setOnClickListener(null);
}