java - Activity和View之间的接口(interface)实现错误

Question

我正在尝试从 View MyView 获取MyActivity 中的int。在我的 Activity 中，我有以下内容:

public class MyActivity extends AppCompatActivity implements MyView.GetCallBack {

    final MyActivity context = this;
    private AsyncTask<Void, Void, Void> task;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_second_act);

        task = new myTask();
        task.execute();

    }

    @Override
    public void onPercentageReceived(int msg){
        // you have got your msg here.
    }

    public class MyTask extends AsyncTask<Void, Void, Void> {
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }
        @Override
        protected Void doInBackground(Void... params) {
        }
        @Override
        protected void onPostExecute(Void result) {

            LinearLayout surface = (LinearLayout) findViewById(R.id.surfaceView);
            surface.addView(new MyView(getApplicationContext()));
            surface.setBackgroundColor(Color.BLACK);
        }

    }

现在MyView包含以下代码:

public class MyView extends View {
    final MyView context = this;     
    private GetCallBack callback;
    // Constructor
    public PlacingBoxView(Context context) {
        super(context);
        callback = (GetCallBack) context;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        dataPercentage(Percentage);
    }

    public void dataPercentage(int Percentage){
        callback.onPercentageReceived(Percentage);
    }


    public interface GetCallBack{
        void onPercentageReceived(int msg);
    }

我可以毫无问题地编译代码，但在 LogCat 中出现以下错误:

FATAL EXCEPTION: main Process: com.example.ex, PID: 8035 java.lang.ClassCastException: android.app.Application cannot be cast to com.example.ex.myView$GetCallBack at com.example.ex.myView.(myView.java:49)

我知道错误与上下文有关，但我仍然没有找到纠正它的方法，

任何想法都会非常感激! :)

Answer 1

您已在 myActivity 中实现了接口(interface)，但您正在传递应用程序上下文。这就是为什么您会收到ClassCastException。传递myActivity.this，所以尝试这样:

surface.addView(new MyView(MyActivity.this);