AsyncTask异常

Question

我是Android开发的初学者,我正在使用我的fisrt应用程序,我遇到了一个问题.我必须下载一些图像投掷互联网,并在活动中显示它们.我有一个UI延迟,直到下载图像,所以我必须使用多线程.

我阅读了更多关于它的内容,我认为最简单的是使用AsyncTask,但我发现了一个异常: Only the original thread that created a view hierarchy can touch its views.

我需要帮助.可以帮助我吗？代码是这样的:

public class Main extends Activity{



protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    Download download = new Download();
    download.execute(null);
}

private class Download extends AsyncTask<String, Void, String>{
    ImageButtonOverloaded[] imgView = new ImageButtonOverloaded[24];
    TextView[] textView = new TextView[24];
    @Override
    protected String doInBackground(String... params) {
        try{

            URL url = null;
            url = new URL(StaticClass.URL_HOST + "front_page_last_games_plaintext.php");
            URLConnection conn = url.openConnection();
            BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;

            initCovers();
            int i = 0;
            Log.d("SYNC", "i = 0");
            while((line = reader.readLine()) != null){
                String gameInfo[] = line.split("<NEXT>");
                //Log.d("SYNC", gameInfo[0]);
                //Log.d("SYNC", gameInfo[1]);
                Drawable x = ImageOperations(Main.this, StaticClass.URL_HOST + "resize.php?imagine=" + gameInfo[0] ,"image.jpg");

                Log.d("SYNC", "in while");
                imgView[i].setImageDrawable(x);
                Log.d("SYNC", "in while");
                imgView[i].setGameID(gameInfo[0]);
                imgView[i].setOnClickListener(new OnClickListener() {

                    public void onClick(View v) {
                        ImageButtonOverloaded temp = (ImageButtonOverloaded) v;
                        Intent intent = new Intent(Main.this, Single.class);
                        intent.putExtra("ID", temp.getGameID());
                        startActivity(intent);

                    }
                });

                textView[i].setText(gameInfo[1]);
                textView[i].setGravity(Gravity.TOP);
                textView[i].setGravity(Gravity.CENTER_HORIZONTAL);
                textView[i].setTextColor(Color.WHITE);
                i++;
            }
        }catch(Exception ex){
            Log.d("SYNC", ex.getMessage());
        }
        return null;
    }
    private Drawable ImageOperations(Context ctx, String url, String saveFilename) {
        try {
            InputStream is = (InputStream) this.fetch(url);
            Drawable d = Drawable.createFromStream(is, "src");
            return d;
        } catch (MalformedURLException e) {
            e.printStackTrace();
            return null;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    public Object fetch(String address) throws MalformedURLException,IOException {
        URL url = new URL(address);
        Object content = url.getContent();
        return content;
    }
    private void initCovers(){
        imgView[0] = (ImageButtonOverloaded) findViewById(R.id.imageButton1);
        imgView[1] = (ImageButtonOverloaded) findViewById(R.id.imageButton2);
        imgView[2] = (ImageButtonOverloaded) findViewById(R.id.imageButton3);
        imgView[3] = (ImageButtonOverloaded) findViewById(R.id.imageButton4);
        imgView[4] = (ImageButtonOverloaded) findViewById(R.id.imageButton5);
        imgView[5] = (ImageButtonOverloaded) findViewById(R.id.imageButton6);
        imgView[6] = (ImageButtonOverloaded) findViewById(R.id.imageButton7);
        imgView[7] = (ImageButtonOverloaded) findViewById(R.id.imageButton8);
        imgView[8] = (ImageButtonOverloaded) findViewById(R.id.imageButton9);
        imgView[9] = (ImageButtonOverloaded) findViewById(R.id.imageButton10);
        imgView[10] = (ImageButtonOverloaded) findViewById(R.id.imageButton11);
        imgView[11] = (ImageButtonOverloaded) findViewById(R.id.imageButton12);
        imgView[12] = (ImageButtonOverloaded) findViewById(R.id.imageButton13);
        imgView[13] = (ImageButtonOverloaded) findViewById(R.id.imageButton14);
        imgView[14] = (ImageButtonOverloaded) findViewById(R.id.imageButton15);
        imgView[15] = (ImageButtonOverloaded) findViewById(R.id.imageButton16);
        imgView[16] = (ImageButtonOverloaded) findViewById(R.id.imageButton17);
        imgView[17] = (ImageButtonOverloaded) findViewById(R.id.imageButton18);
        imgView[18] = (ImageButtonOverloaded) findViewById(R.id.imageButton19);
        imgView[19] = (ImageButtonOverloaded) findViewById(R.id.imageButton20);
        imgView[20] = (ImageButtonOverloaded) findViewById(R.id.imageButton21);
        imgView[21] = (ImageButtonOverloaded) findViewById(R.id.imageButton22);
        imgView[22] = (ImageButtonOverloaded) findViewById(R.id.imageButton23);
        imgView[23] = (ImageButtonOverloaded) findViewById(R.id.imageButton24);

        textView[0] = (TextView) findViewById(R.id.textView1);
        textView[1] = (TextView) findViewById(R.id.textView2);
        textView[2] = (TextView) findViewById(R.id.textView3);
        textView[3] = (TextView) findViewById(R.id.textView4);
        textView[4] = (TextView) findViewById(R.id.textView5);
        textView[5] = (TextView) findViewById(R.id.textView6);
        textView[6] = (TextView) findViewById(R.id.textView7);
        textView[7] = (TextView) findViewById(R.id.textView8);
        textView[8] = (TextView) findViewById(R.id.textView9);
        textView[9] = (TextView) findViewById(R.id.textView10);
        textView[10] = (TextView) findViewById(R.id.textView11);
        textView[11] = (TextView) findViewById(R.id.textView12);
        textView[12] = (TextView) findViewById(R.id.textView13);
        textView[13] = (TextView) findViewById(R.id.textView14);
        textView[14] = (TextView) findViewById(R.id.textView15);
        textView[15] = (TextView) findViewById(R.id.textView16);
        textView[16] = (TextView) findViewById(R.id.textView17);
        textView[17] = (TextView) findViewById(R.id.textView18);
        textView[18] = (TextView) findViewById(R.id.textView19);
        textView[19] = (TextView) findViewById(R.id.textView20);
        textView[20] = (TextView) findViewById(R.id.textView21);
        textView[21] = (TextView) findViewById(R.id.textView22);
        textView[22] = (TextView) findViewById(R.id.textView23);
        textView[23] = (TextView) findViewById(R.id.textView24);

    }
}}

Answer 1

doInBackgorund()是一个非UI线程,您无法访问其中的UI元素.doInBackground()中的代码在一个单独的非ui线程上运行,该线程无法访问布局中定义的UI元素.此外,由于您通过意图调用另一个Activity,因此您应该始终牢记一个Activity在UI线程上运行,因此您永远不应该从非ui线程中启动另一个Activity.

因此,从doInBackground()内部删除访问UI元素的代码,然后将其放入内部onPostExecute(),这是一个UI线程,并在doInBackground()完成后台处理后调用.

int i =0; // global variable
Drawable drawableArray []; // global array to store all the drawables 

doInBackground(String... params) {
        try{

            URL url = null;
            url = new URL(StaticClass.URL_HOST + "front_page_last_games_plaintext.php");
            URLConnection conn = url.openConnection();
            BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;

            initCovers();
            while((line = reader.readLine()) != null){
                String gameInfo[] = line.split("<NEXT>");
                //Log.d("SYNC", gameInfo[0]);
                //Log.d("SYNC", gameInfo[1]);
                drawableArray[i] = ImageOperations(Main.this, StaticClass.URL_HOST + "resize.php?imagine=" + gameInfo[0] ,"image.jpg");
                i++;
}

onPostExecute()
{
   for(j=0;j<=i;j++)

                Log.d("SYNC", "in while");
                imgView[j].setImageDrawable(drawableArray[j]);
                Log.d("SYNC", "in while");
                imgView[j].setGameID(gameInfo[0]);
                imgView[j].setOnClickListener(new OnClickListener() {

                    public void onClick(View v) {
                        ImageButtonOverloaded temp = (ImageButtonOverloaded) v;
                        Intent intent = new Intent(Main.this, Single.class);
                        intent.putExtra("ID", temp.getGameID());
                        startActivity(intent);

                    }
                });

                textView[j].setText(gameInfo[1]);
                textView[j].setGravity(Gravity.TOP);
                textView[j].setGravity(Gravity.CENTER_HORIZONTAL);
                textView[j].setTextColor(Color.WHITE);
                j++;
            }
}

编辑:正如@Luksprog和@tolgap指出的那样,主ui线程上的图像处理部分是运算良好的,可能会使UI无响应.因此,最好也在后台线程上进行图像处理,然后使用onPostExecute()来设置图像位图并更新其他UI元素.使用全局数组通过在后台进行处理来存储Drawables,然后只需更新onPostExecute()中的UI.