android - 从 onActivityResult 调用的 onPostExecute 更新 fragment 的 UI

Question

在我的应用程序中，我通过点击按钮选择文档来启动带有 ACTION_OPEN_DOCUMENT 的 Intent 。

private static final int READ_REQUEST_CODE = 42;
public void performFileSearch() {

    // ACTION_OPEN_DOCUMENT is the intent to choose a file via the system's file
    // browser.
    Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
    intent.addCategory(Intent.CATEGORY_OPENABLE);
    intent.setType("*/*");
    String[] mimeTypes = {
            "image/*",
            "text/plain",
            "application/pdf"
    };
    intent.putExtra(Intent.EXTRA_MIME_TYPES, mimeTypes);
    startActivityForResult(intent, READ_REQUEST_CODE);
}

之后，我在 onActivityResult 中获取用户选择的文档的 Uri 并将其传递给一个 AsyncTask文档已压缩。

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == READ_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
        if (data != null) {
            dialog = new ProgressDialog(getActivity());
            dialog.setMessage(getString(R.string.upload_dialog));
            dialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
            dialog.setIndeterminate(true);
            dialog.setCancelable(false);
            dialog.show();

            // The document selected by the user won't be returned in the intent.
            // Instead, a URI to that document will be contained in the return intent
            // provided to this method as a parameter.
            // Pull that URI using resultData.getData().
            new ZipFile().execute(data.getData());
        }
    }
}

下面是我的 AsyncTask 类:

private class ZipFile extends AsyncTask<Uri, Void, String> {

    @Override
    protected String doInBackground(Uri... uris) {
        Uri uri = uris[0];
        String fileName = null;

        try {
            fileName = zm.createPath("user");
            zm.zipFromUri(uri, fileName, commonMethods.getFileName(uri));
        } catch (NullPointerException | IOException e) {
            e.printStackTrace();
        }
        return fileName;
    }

    @Override
    protected void onPostExecute(String fileName) {
        dialog.dismiss();
        if (fileName != null) {
            renderView(view);
        }
    }
}

在 renderView 函数中，我显示了一个 snackbar 并更新了 fragment 的 UI。

private void renderView(View view) {

    CoordinatorLayout fileSnackbarView = view.findViewById(R.id.filesCoordinatorLayout);

    //Exception at this line
    fileSnackbar = Snackbar.make(fileSnackbarView, String.format(getResources().getString(R.string.snackbarMessage), FILE_COUNT), Snackbar.LENGTH_INDEFINITE)
            .setAction(getResources().getString(R.string.snackbarAction), new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent intent = new Intent(getActivity(), ViewSelectedFilesActivity.class);
                    Bundle bundle = new Bundle();
                    ArrayList<String> selectedFileName = new ArrayList<>();
                    selectedFileName.add(commonMethods.getFromPreferences(Constants.originalFileNameKey, "string"));
                    bundle.putStringArrayList("fileList", selectedFileName);
                    intent.putExtras(bundle);
                    startActivity(intent);
                }
            });
    ... code        
}

但是，我的应用程序崩溃并出现异常 Fragment not attached to a context。下面是完整的堆栈跟踪:

03-08 12:09:20.647 11490-11490/com.zeetim.zeeprintmobile.android E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.zeetim.zeeprintmobile.android, PID: 11490
java.lang.IllegalStateException: Fragment HomeFragment{674af0} not attached to a context.
    at android.support.v4.app.Fragment.requireContext(Fragment.java:611)
    at android.support.v4.app.Fragment.getResources(Fragment.java:675)
    at com.zeetim.zeeprintmobile.fragment.HomeFragment.renderView(HomeFragment.java:287)
    at com.zeetim.zeeprintmobile.fragment.HomeFragment.access$700(HomeFragment.java:51)
    at com.zeetim.zeeprintmobile.fragment.HomeFragment$ZipFile.onPostExecute(HomeFragment.java:595)
    at com.zeetim.zeeprintmobile.fragment.HomeFragment$ZipFile.onPostExecute(HomeFragment.java:563)
    at android.os.AsyncTask.finish(AsyncTask.java:695)
    at android.os.AsyncTask.-wrap1(Unknown Source:0)
    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:712)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6494)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

在一些调试中，我发现 isAdded() 返回 false 和 getActivity(), getContext() 是 null。

流程似乎非常简单，但行不通。那么我在这方面有什么遗漏吗？
如何从 onActivityResult 调用的 onPostExecute 更新 fragment 的 UI？

谢谢。

Answer 1

在 onPostExecute 中试试这个

   new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {

           //if(isAdded()) {
            if (fileName != null) {
                renderView(view);
            }
         }

       // }
    },300);