区分Handler和HandlerThread

Handler实例可以在主线程创建，也可以在子线程创建。
在子线程中创建时通过Looper，以下示例：

public class MainActivity extends AppCompatActivity {
    HandlerThread handlerThread;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
         handlerThread = new HandlerThread("子线程");
         handlerThread.start();
        Looper looper = handlerThread.getLooper();
        final Handler handler = new Handler(looper) {
            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
                Log.d("----->", "线程:" + Thread.currentThread().getName());
            }
        };
        findViewById(R.id.bt).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                handler.sendEmptyMessage(100);
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        handlerThread.quit();

    }
}

HandlerThread用法