我如何在ListView中執行AsyncTask

Question

我想添加ListView，因為現在它只能看到textview。 這是主要活動和activity_main

主要活動

public class MainActivity extends AppCompatActivity
{
    private TextView txtResult;
    private Button btnItem;
    private Button btnItemList;
    private ListView myListView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);


        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        txtResult = (TextView) findViewById(R.id.txt_result);
        btnItem = (Button) findViewById(R.id.btn_item);
        btnItemList = (Button) findViewById(R.id.btn_item_list);

        btnItem.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                new GetItemTask().execute();
            }
        });

        btnItemList.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                new GetItemListTask().execute();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private void setResult(Post post) {
        txtResult.setText(post.getName());
    }

    private void setResult(ArrayList<Post> posts) {
        for (Post post : posts) {
            txtResult.append(post.getName());
        }
    }


    private class GetItemTask extends AsyncTask<Void, Void, String> {
        HttpURLConnection urlConnection;

        @Override
        protected String doInBackground(Void... params) {
            StringBuilder result = new StringBuilder();
            try {
                URL url = new URL("https://jsonplaceholder.typicode.com/users/1");
                urlConnection = (HttpURLConnection) url.openConnection();
                InputStream in = new BufferedInputStream(urlConnection.getInputStream());
                BufferedReader reader = new BufferedReader(new InputStreamReader(in));

                String line;
                while ((line = reader.readLine()) != null) {
                    result.append(line);
                }

            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                urlConnection.disconnect();
            }

            return result.toString();
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            Post post = new Gson().fromJson(s, Post.class);
            setResult(post);
        }
    }

    private class GetItemListTask extends AsyncTask<Void, Void, String> {
        HttpURLConnection urlConnection;

        @Override
        protected String doInBackground(Void... params) {
            StringBuilder result = new StringBuilder();
            try {
                URL url = new URL("https://jsonplaceholder.typicode.com/users");
                urlConnection = (HttpURLConnection) url.openConnection();
                InputStream in = new BufferedInputStream(urlConnection.getInputStream());
                BufferedReader reader = new BufferedReader(new InputStreamReader(in));

                String line;
                while ((line = reader.readLine()) != null) {
                    result.append(line);
                }

            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                urlConnection.disconnect();
            }

            return result.toString();
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            ArrayList<Post> posts = new Gson().fromJson(s,
                    new TypeToken<ArrayList<Post>>() {
                    }.getType());
            setResult(posts);
        }
    }
}

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>


    <android.support.design.widget.CoordinatorLayout                xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="etts.gsontest.MainActivity">



    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true"
        android:layout_alignParentEnd="true" />

</android.support.design.widget.CoordinatorLayout>

這是我的應用

Answer 1

這可能對您有幫助：

public void populateListView(ArrayList<String> myData){

    myListView = (ListView) findViewById(R.id.listView);

    //Creating an array adapter and populating it with data fetched in Async task i.e. myData
     ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(
             this, 
             android.R.layout.simple_list_item_1,
             myData );

    //Setting the array adapter to your list view
     myListView.setAdapter(arrayAdapter); 
}

然后可以從OnPostExecute（）方法中調用此方法。

Answer 2

在OnCreate方法中初始化ListView

listView = (ListView) findViewById(R.id.listView);

AsyncTask PostExceute方法

ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(
         this, 
         android.R.layout.simple_list_item_1,
         myData );

 listView.setAdapter(arrayAdapter);