Question

这是我的MainActivity，我想要在AsyncTask类中处理进度对话框，但是将上下文传递给asyncTask似乎无法正常工作并且应用程序崩溃时出现NullPointerException错误，如果我尝试在MainActivity中设置progressDialog，然后获取引用在使用mContext.progress的AsyncTask中，应用程序因WindowLeaked错误而崩溃。

public class MainActivity extends Activity{

ConnectionHandler ch;
SearchForCard mTask = null;
String finalUrl = "";
Button searchBtn;

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

    ch = new ConnectionHandler(this);

    searchBtn.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
                mTask = ch.new SearchForCard();
                mTask.execute(finalUrl);
            }

        }
    });

}

在我的ConnectionHandler类中，我希望为我必须做的每一件事创建单独的asynctask，请不要在MainActivity中为内部Asynctask提供解决方案，这不是我想要做的事情

public class ConnectionHandler{

private MainActivity mContext;
Handler mHandler = new Handler();
Document doc = null;
Elements title = null;
String response = null;
ProgressDialog progress;

public ConnectionHandler(MainActivity ctx)
{
    mContext = ctx;

    progress = new ProgressDialog(mContext); <--APPLICATION CRASH HERE WITH DEBUGGER
    progress.setTitle("loading");
    progress.setIndeterminate(false);

}

public class SearchForCard extends AsyncTask<String, Void, Boolean> {


    @Override
    protected void onPreExecute() {

        progress.show();

        super.onPreExecute();
    }

    @Override
    protected Boolean doInBackground(String... url) {

        try{
            doc = Jsoup.connect(url[0]).get();
            Log.d("RESPONSE",doc.toString());
        } catch (Exception e){
            e.printStackTrace();
        }

        return false;
    }

     @Override
        protected void onPostExecute(Boolean result) {

            super.onPostExecute(result);

            progress.dismiss();

        }
}
}

我做错了什么？感谢

这是错误：

02-08 12:40:28.275: E/WindowManager(3574): Activity com.pagiodevelop.MainActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@5371c7b4 that was originally added here
02-08 12:40:28.275: E/WindowManager(3574): android.view.WindowLeaked: Activity com.pagiodevelop.MainActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@5371c7b4 that was originally added here
02-08 12:40:28.275: E/WindowManager(3574):  at android.view.ViewRootImpl.<init>(ViewRootImpl.java:374)
02-08 12:40:28.275: E/WindowManager(3574):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:292)
02-08 12:40:28.275: E/WindowManager(3574):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:224)
02-08 12:40:28.275: E/WindowManager(3574):  at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:149)
02-08 12:40:28.275: E/WindowManager(3574):  at android.view.Window$LocalWindowManager.addView(Window.java:547)
02-08 12:40:28.275: E/WindowManager(3574):  at android.app.Dialog.show(Dialog.java:277)
02-08 12:40:28.275: E/WindowManager(3574):  at com.pagiodevelop.ConnectionHandler$SearchForCard.onPreExecute(ConnectionHandler.java:40)
02-08 12:40:28.275: E/WindowManager(3574):  at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
02-08 12:40:28.275: E/WindowManager(3574):  at android.os.AsyncTask.execute(AsyncTask.java:534)
02-08 12:40:28.275: E/WindowManager(3574):  at com.pagiodevelop.MainActivity$1.onClick(MainActivity.java:50)
02-08 12:40:28.275: E/WindowManager(3574):  at android.view.View.performClick(View.java:4084)
02-08 12:40:28.275: E/WindowManager(3574):  at android.view.View$PerformClick.run(View.java:16966)
02-08 12:40:28.275: E/WindowManager(3574):  at android.os.Handler.handleCallback(Handler.java:615)
02-08 12:40:28.275: E/WindowManager(3574):  at android.os.Handler.dispatchMessage(Handler.java:92)
02-08 12:40:28.275: E/WindowManager(3574):  at android.os.Looper.loop(Looper.java:137)
02-08 12:40:28.275: E/WindowManager(3574):  at android.app.ActivityThread.main(ActivityThread.java:4745)
02-08 12:40:28.275: E/WindowManager(3574):  at java.lang.reflect.Method.invokeNative(Native Method)
02-08 12:40:28.275: E/WindowManager(3574):  at java.lang.reflect.Method.invoke(Method.java:511)
02-08 12:40:28.275: E/WindowManager(3574):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
02-08 12:40:28.275: E/WindowManager(3574):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-08 12:40:28.275: E/WindowManager(3574):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

使用进度对话框和异步任务时，这应该是正确的解决方案

public static class SearchForCard extends AsyncTask<String, Void, Boolean> {

    private Context mContext;
    private ProgressDialog mProgress;

    public SearchForCard (Context context) {
        mContext = context;
    } 

    @Override
    protected void onPreExecute() {
        mProgress = new ProgressDialog(mContext);
        //customize the progress dialog here
        mProgress.setCancelable(false);
        mProgress.show();
    }

    @Override
    protected Boolean doInBackground(String... url) {
        //do your background work and return something
        return false;
    }

    @Override
    protected void onPostExecute(Boolean result) {
        if (mProgress != null && mProgress.isShowing())
            mProgress.dismiss();

        //evaluate result
    }
}

android处理进度对话框在一个单独的异步任务类中

1 个答案: