java - 无法将 JSON 数据发送到其他 Android Activity

Question

我对 Android 还很陌生。我正在尝试做的事情:我通过API下载了JSON格式的数据。我正在尝试将其与其他一些数据 bundle 在一起并将其发送到我的第二个 Activity 。我背后的逻辑是，我创建了一个全局变量“JSONData”，并将我在“onPostExecute”中下载的数据分配给它。但是，当我尝试通过 Intent ( bundle )将其发送到第二个 Activity 时，仅显示第一条数据。我的猜测是，该包是在下载 JSON 数据之前发送的。数据肯定是通过 API 下载的，因为我使用 TextView 显示它。任何人都可以给我一些关于如何解决这个问题的提示吗？我将非常感激:)

public class MainActivity extends AppCompatActivity {
private String JSONData;
private TextView Data_Test;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    TestView = (TextView)findViewById(R.id.TestView);
}

public class JSONTask extends AsyncTask<String, String, String> {

    @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);
        JSONData = result;
        /*Data_Test.setText(JSONData);*/


    }
}


public void btnType0(View view) {
    new JSONTask().execute("URL_with_API");
    String activity_title = getResources().getString(R.string.housing_button);
    Intent intent = new Intent(this, DisplayDataActivity.class);
    Bundle extras = new Bundle();
    extras.putString("title", activity_title);
    extras.putString("JSON_Object", JSONData);
    intent.putExtras(extras);
    startActivity(intent);
}

在我的第二个 Activity 中，我收到了这样的 bundle :

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_display_data);

    Bundle bundle = getIntent().getExtras();

    String activity_title = bundle.getString("title");
    TextView txtView = (TextView) findViewById(R.id.txtTitle);
    txtView.setText(activity_title);

    String JSONData = bundle.getString("JSON_Object");
    TextView txtView1 = (TextView) findViewById(R.id.data_test);
    txtView1.setText(JSONData);

}

Answer 1

哥们，你做错了!!

new JSONTask().execute("URL_with_API"); 您无法在 JSONData 变量中获取值，因为您已将其声明为全局变量，并且在 AsyncTask 中分配值这是后台进程，因此这一行将进入后台，下一行将立即执行。下面

String activity_title = getResources().getString(R.string.housing_button);
Intent intent = new Intent(this, DisplayDataActivity.class);
Bundle extras = new Bundle();
extras.putString("title", activity_title);
extras.putString("JSON_Object", JSONData);// so here JSONData always being null
intent.putExtras(extras);
startActivity(intent);

您必须像这样在 onPostExecute 中启动 Activity

@Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        String activity_title = getResources().getString(R.string.housing_button);
        Intent intent = new Intent(this, DisplayDataActivity.class);
        Bundle extras = new Bundle();
        extras.putString("title", activity_title);
        extras.putString("JSON_Object", result);
        intent.putExtras(extras);
        startActivity(intent);
    }



public void btnType0(View view) {
    new JSONTask().execute("URL_with_API");
}

Or just pass Url in required activity and fetch data in that activity using url in onCreate