Handlerthread使用

public class MainActivity extends AppCompatActivity {

    TextView textView;
    Button button;
    MainHandler mainHandler;
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = findViewById(R.id.text);
        button = findViewById(R.id.button);
        //这个是主线程Handler 实例 还有一个知识点就是如果new Handler时候没有给她传递looper的话，他会默认的去当前运行线程的looper进行联系
        mainHandler = new MainHandler(this);


        HandlerThread handlerThread = new HandlerThread("first");
        handlerThread.start();
        //这是子线程联系的handler 传入了handlerThread的looper
        final Handler childHandler = new Handler(handlerThread.getLooper()) {
            int count = 0;

            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
                System.out.println("子线程 的handler 接受到数据  现在 将数据发送给 主线程 执行 " + Thread.currentThread().getName());
                //发送消息给 主线程的handler 让她更新ui
                Message.obtain(mainHandler, 1, ++count).sendToTarget();
            }
        };


        // 开启一个子线程 调用childHandler 发送信息
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        System.out.println("子线程发送数据 " + Thread.currentThread().getName());
                        //发送给handlerThread的handler
                        childHandler.sendEmptyMessage(1);
                    }
                }).start();
            }
        });

    }
        //这个是主线程的Handler 定义成这种形式，可以防止内存泄露
        class MainHandler extends Handler {
            private WeakReference<MainActivity> mainActivityWeakReference;

            MainHandler(MainActivity mainActivity) {
                this.mainActivityWeakReference = new WeakReference<>(mainActivity);
            }

            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
                mainActivityWeakReference.get().textView.setText(msg.obj + "");
            }
        }
    }