如何在课堂上的成功回调中调用 toast 消息

Question

我正在使用 okhttp 库开发 POST API。一切工作正常，除了我无法找到一种方法来在它的成功回调上显示一个简单的 toast 消息。如何向用户调用 toast 消息，以便他知道数据是否已发布到服务器上，或者是否在成功和失败回调中？

P.S 下面的代码在不同的类中，而不是在活动类中。

这是我的代码：

public DataSource(Context context) {
    this.mContext = context;
    mDbHelper = new DBHelper(mContext);
    mDatabase = mDbHelper.getWritableDatabase();
}



    post(URL, jsonData, new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                Log.i("FAILED", "onFailure: Failed to upload data to server");
                //here I want to show toast message
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                if (response.isSuccessful()) {

                    Log.i("SUCCESSFUL", "onSuccess: data uploaded");

                    //here I want to show toast message

                } else {
                    Log.i("UN SUCCESSFUL", "onFailure: Failed to upload data to server");
                    //here I want to show toast message
                }
            }
       });

Answer 1

每个应用程序都有自己的特殊线程来运行 UI 对象，例如 View 对象；这个线程称为 UI 线程。只有在 UI 线程上运行的对象才能访问该线程上的其他对象。因为您在线程池中的线程上运行的任务不在您的 UI 线程上运行，所以它们无权访问 UI 对象。要将数据从后台线程移动到 UI 线程，请使用在 UI 线程上运行的 Handler，或者可以使用 android 实现，如此处所示。

- 案例 1

 MyActivity.this.runOnUiThread(new Runnable() {
            @Override
            void run() {
               Toast.makeText(MyActivity.this,
                    "message", Toast.LENGTH_LONG).show();
            });

- 案例 2

new Handler(Looper.getMainLooper()).post(new Runnable() {
    @Override
    public void run() {
       Toast.makeText(MyActivity.this,
                    "message", Toast.LENGTH_LONG).show();
    }
});

如果它是主线程，你会直接使用它

Toast.makeText(MyActivity.this,
                    "message", Toast.LENGTH_LONG).show();

Answer 2

这个回调是一个异步函数，你可以在UI线程中改变View，所以Handler会为你提供帮助。

    ....
    private final static int MSG_SUCCESS = 0x0001;
    private final static int MSG_FAIL = 0x0002;
    private Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch(msg.what){
              case MSG_SUCCESS:
                 //Toast success
                  break;
              case MSG_FAIL:
                 //Toast fail
                  break;
              default:
                  break;
            }
        }
    };

    ......
    ......

    if (response.isSuccessful()) {
              Log.i("SUCCESSFUL", "onSuccess: data uploaded");
              handler.sendEmptyMessage(MSG_SUCCESS);
           } else {
             Log.i("UN SUCCESSFUL", "onFailure: Failed to upload data to server");
              handler.sendEmptyMessage(MSG_FAIL);
            }
     ......

Answer 3

你遇到了错误

java.lang.RuntimeException：无法在线程内创建处理程序 没有调用 Looper.prepare()

因为您是从工作线程调用它。您需要从主线程中调用Toast.makeText()（以及处理 UI 的大多数其他函数）。您可以使用处理程序，

 @Override
 public void onResponse(Call call, Response response) throws IOException {
                if (response.isSuccessful()) {    
                    Log.i("SUCCESSFUL", "onSuccess: data uploaded");

                    context.runOnUiThread(new Runnable() {
                    public void run() {
                    Toast.makeText(context, "SUCCESSFUL", Toast.LENGTH_SHORT).show();
                     }
                  });
                }

Answer 4

只需在调用此方法时发送您的活动上下文：

void methodName(Context c){

 post(URL, jsonData, new Callback() {
                @Override
                public void onFailure(Call call, IOException e) {
                    Log.i("FAILED", "onFailure: Failed to upload data to server");
                    //here I want to show toast message
                }

                @Override
                public void onResponse(Call call, Response response) throws IOException {
                    if (response.isSuccessful()) {

                        Log.i("SUCCESSFUL", "onSuccess: data uploaded");
                       Toast.makeText(c,"message",Toast.LENGTH_SHORT).show();
                        //here I want to show toast message

                    } else {
                        Log.i("UN SUCCESSFUL", "onFailure: Failed to upload data to server");
                        //here I want to show toast message
                    }
                }
});
}

Answer 5

试试这个

TaskActivity.this.runOnUiThread(new Runnable() {
        @Override
        void run() {
            Toast msg = Toast.makeText(TaskActivity.this,
                "message", Toast.LENGTH_LONG);
            msg.show();
        });

Answer 6

试试这个

Toast.makeText(YourActivity.this, "Your Message", Toast.LENGTH_SHORT).show();

活动

post(URL, jsonData, new Callback() {
                    @Override
                    public void onFailure(Call call, IOException e) {
                        Log.i("FAILED", "onFailure: Failed to upload data to server");
                        //here I want to show toast message
                        Toast.makeText(YourActivity.this, "Your Message", Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void onResponse(Call call, Response response) throws IOException {
                        if (response.isSuccessful()) {

                            Log.i("SUCCESSFUL", "onSuccess: data uploaded");

                            //here I want to show toast message
                            Toast.makeText(YourActivity.this, "Your Message", Toast.LENGTH_SHORT).show();

                        } else {
                            Log.i("UN SUCCESSFUL", "onFailure: Failed to upload data to server");
                            //here I want to show toast message
                            Toast.makeText(YourActivity.this, "Your Message", Toast.LENGTH_SHORT).show();
                        }
                    }
   });

片段

post(URL, jsonData, new Callback() {
                    @Override
                    public void onFailure(Call call, IOException e) {
                        Log.i("FAILED", "onFailure: Failed to upload data to server");
                        //here I want to show toast message
                        Toast.makeText(getActivity(), "Your Message", Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void onResponse(Call call, Response response) throws IOException {
                        if (response.isSuccessful()) {

                            Log.i("SUCCESSFUL", "onSuccess: data uploaded");

                            //here I want to show toast message
                            Toast.makeText(getActivity(), "Your Message", Toast.LENGTH_SHORT).show();

                        } else {
                            Log.i("UN SUCCESSFUL", "onFailure: Failed to upload data to server");
                            //here I want to show toast message
                            Toast.makeText(getActivity(), "Your Message", Toast.LENGTH_SHORT).show();
                        }
                    }
   });

编辑

Handler handler = new Handler();

handler.runOnUiThread(new Runnable() {
  public void run() {
    Toast.makeText(mContext, "Your Message", Toast.LENGTH_SHORT).show();
  }
});