Question

在我的Android应用程序中，我有一个MainActivity类，它启动一个Thread。这个线程做了Stuff并在屏幕上显示它。（这部分正在运作）

从线程我想访问MainActivity-Class中的方法。但它不起作用......＆＃34;无法解决方法＆＃34;

这是我的代码......

线程对象：

public class SensorProcessor implements Runnable {

    protected Context mContext;
    protected Activity mActivity;

    private volatile boolean running = true;
    //Tag for Logging
    private final String LOG_TAG = SensorProcessor.class.getSimpleName();

    public SensorProcessor(Context mContext, Activity mActivity){
        this.mContext = mContext;
        this.mActivity = mActivity;
    }


    public void run() {

            while (running){

                try {                    

                    final String raw = getSensorValue();
                    mActivity.runOnUiThread(new Runnable() {
                        public void run() {
                            //WORKS
                            final TextView textfield_sensor_value;
                            textfield_sensor_value = (TextView) mActivity.findViewById(R.id.text_sensor);
                            textfield_sensor_value.setText("Sensor Value: " + raw);
                            Log.v(LOG_TAG, raw);


                            //DOES NOT WORK, WHY?
                            mActivity.myMethod(); //Cannot resolve method
                        }
                    });



                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    //When an interrupt is called, we set running to false, so the thread can exit nicely
                    running = false;
                }
            }

            Log.v(LOG_TAG, "Sensor Thread finished");

    }
}

MainActivity类，调用线程：

public class MainActivity extends Activity implements OnClickListener, OnInitListener {


    public void myMethod(){
        //Do stuff...
    }

    //Start the Thread, when the button is clicked
    public void onClick(View v) {
        if (v.getId() == R.id.button_start) {
            runnable = new SensorProcessor(this.getApplicationContext(),this);
            thread = new Thread(runnable);
            thread.start();
        }
    }
}

为什么它不起作用，使用mActivity.runOnUiThread（new Runnable（） - Approach，以及如何正确完成？

祝你好运

Answer 1

使用mActivity类型MainActivity输入((MainActivity)mActivity)。但请确保您不应该从线程更新UI。

Answer 2

你需要使用一个Handler才能在线程和ui-thread（你的活动）之间进行交互所以这就是我要做的。

    public class SensorProcessor implements Runnable {

        protected Context mContext;
        protected Handler handler;

        private volatile boolean running = true;
        //Tag for Logging
        private final String LOG_TAG = SensorProcessor.class.getSimpleName();

      // here I pass a handler instead of activity
        public SensorProcessor(Context mContext, Handler handler){ 
            this.mContext = mContext;
            this.handler = handler;
        }

    // here is the key. Replace  mActivity.myMethod(); with the following
    handler.sendEmptyMessage(randomIntegerNumberWhatever);
    ...etc etc

然后创建一个像dat一样的自定义处理程序

public class MessageHandler extends Handler
{
    public interface IHandler
    {
        void myMethod();
    }

    private final IHandler activityHandler;

    public MessageHandler(IHandler listener)
    {
        activityHandler = listener;
    }

    @Override
    public void handleMessage(Message msg)
    {
        super.handleMessage(msg);
        if (msg.what == randomIntegerNumberWhatever)
        {
            activityHandler.myMethod();
        }
    }
}

然后让您的活动实现MessageHandler.IHandler接口。它可能看起来很复杂，但它可以信任我

Answer 3

基本myMethod()类中不存在

Activity，因此强制转换为（或提供）MainActivity

Answer 4

Activity类不包含myMethod()函数。您需要将数据类型更改为具有此功能的特定活动：

protected MainActivity mActivity;

public SensorProcessor(Context mContext, MainActivity mActivity){
    this.mContext = mContext;
    this.mActivity = mActivity;
}

从Thread-Object访问MainActivity中的方法

4 个答案: