从MainActivity Class访问私有字段到另一个类

I have declared a private field in the MainActivity Class with getter and setter method. Now I want to setText from another class in this field. But after running the device the app is crushing. I want to fetch some json data by using this code. I am not getting how to call this field from another class and how to set the value to run the app smoothly. My code looks like this.

我已经使用getter和setter方法在MainActivity类中声明了一个私有字段。现在我想从这个字段中的另一个类setText。但在运行设备后,应用程序正在破碎。我想通过使用此代码获取一些json数据。我没有得到如何从另一个类调用此字段以及如何设置值以顺利运行应用程序。我的代码看起来像这样。

public class MainActivity extends AppCompatActivity { 
private TextView tvData;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Button btnHit=(Button)findViewById(R.id.btnHit);
    tvData=(TextView)findViewById(R.id.tvJsonItem);


    btnHit.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            JSONTask jsonTask=new JSONTask("https://jsonparsingdemo-cec5b.firebaseapp.com/jsonData/moviesDemoItem.txt"); //error showing this cannot be applied
            jsonTask.execute();

        }
    });

}

The another class is

另一堂课是

  public class JSONTask extends AsyncTask<String,String,String>{
 private TextView tvData;

 public JSONTask(TextView tvData) {
    this.tvData =tvData;
 }

 @Override
 protected String doInBackground(String... params) {
    HttpURLConnection connection = null;
    BufferedReader reader = null;

    try {
        URL url = new URL(params[0]);
        connection = (HttpURLConnection) url.openConnection();
        connection.connect();
        InputStream stream = connection.getInputStream();

        reader = new BufferedReader(new InputStreamReader(stream));

        StringBuffer buffer = new StringBuffer();

        String line = "";

        while ((line = reader.readLine()) != null) {
            buffer.append(line);
        }
       return buffer.toString();


    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (connection != null) {
            connection.disconnect();
        }
        try {
            if (reader != null) {
                reader.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return null;
 }


 @Override
 protected void onPostExecute(String result) {
    super.onPostExecute(result);
    tvData.setText(result);
  }
}

2 个解决方案

#1

Make your AsyncTask like this:

使你的AsyncTask像这样:

class JSONTask extends AsyncTask<String ,String,String>{
private TextView textView;

public JSONTask(TextView textView) {
    this.textView = textView;
}

@Override
protected String doInBackground(String... params) {
    return null;
}

@Override
protected void onPostExecute(String s) {
    super.onPostExecute(s);
    textView.setText(s);
}

}

now call this class from MainActivity

现在从MainActivity中调用此类

JSONTask jsonTask = new JSONTask(yourTextView);
    jsonTask.execute();

#2

Hope it will work for you .

希望它对你有用。

 @override
   protected void onPostExecute(String result){
      super.onPostExecute(result);
      new MainActivity().setTvData().setText(result);

Use setTvData().setText() to set the value if you only one data in your json string .

如果json字符串中只有一个数据,请使用setTvData()。setText()设置值。

#1