Android studio标准列表视图：E / AndroidRuntime：FATAL EXCEPTION：AsyncTask＃1

时间：2018-05-20 20:52:54

标签： android listview android-asynctask

我正在尝试获取一个简单的列表视图，并遵循https://developer.android.com/guide/topics/ui/layout/listview上的标准ListView。 只有当我按下MainActivity中的按钮时，应用程序才会关闭，我会收到您可以在logcat中看到的消息。我刚开始编程java并使用android studio，所以我可能会做一些完全错误的事情。有谁知道我的问题是什么，并且可能如何解决它？

我的主要活动：

package com.wouterdesigns.a8383;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

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

    Button button = findViewById(R.id.switchbutton);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            switchToListView();
        }
    });
}

public void switchToListView(){
    Intent i = new Intent(this, ListViewLoader.class);
    startActivity(i);
}

}

我的ListViewLoader：

package com.wouterdesigns.a8383;

import android.app.ListActivity;
import android.app.LoaderManager;
import android.content.CursorLoader;
import android.content.Loader;
import android.database.Cursor;
import android.os.Bundle;
import android.provider.ContactsContract;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.SimpleCursorAdapter;

public class ListViewLoader extends ListActivity
    implements LoaderManager.LoaderCallbacks<Cursor> {

// This is the Adapter being used to display the list's data
SimpleCursorAdapter mAdapter;

// These are the Contacts rows that we will retrieve
static final String[] PROJECTION = new String[] {ContactsContract.Data._ID,
        ContactsContract.Data.DISPLAY_NAME};

// This is the select criteria
static final String SELECTION = "((" +
        ContactsContract.Data.DISPLAY_NAME + " NOTNULL) AND (" +
        ContactsContract.Data.DISPLAY_NAME + " != '' ))";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Create a progress bar to display while the list loads
    ProgressBar progressBar = new ProgressBar(this);
    progressBar.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT,
            LinearLayout.LayoutParams.WRAP_CONTENT, Gravity.CENTER));
    progressBar.setIndeterminate(true);
    getListView().setEmptyView(progressBar);

    // Must add the progress bar to the root of the layout
    ViewGroup root = (ViewGroup) findViewById(android.R.id.content);
    root.addView(progressBar);

    // For the cursor adapter, specify which columns go into which views
    String[] fromColumns = {ContactsContract.Data.DISPLAY_NAME};
    int[] toViews = {android.R.id.text1}; // The TextView in simple_list_item_1

    // Create an empty adapter we will use to display the loaded data.
    // We pass null for the cursor, then update it in onLoadFinished()
    mAdapter = new SimpleCursorAdapter(this,
            android.R.layout.simple_list_item_1, null,
            fromColumns, toViews, 0);
    setListAdapter(mAdapter);

    // Prepare the loader. Either re-connect with an existing one,
    // or start a new one.
    getLoaderManager().initLoader(0, null, this);
}

// Called when a new Loader needs to be created
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    // Now create and return a CursorLoader that will take care of
    // creating a Cursor for the data being displayed.
    return new CursorLoader(this, ContactsContract.Data.CONTENT_URI,
            PROJECTION, SELECTION, null, null);
}

// Called when a previously created loader has finished loading
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
    // Swap the new cursor in. (The framework will take care of closing the
    // old cursor once we return.)
    mAdapter.swapCursor(data);
}

// Called when a previously created loader is reset, making the data unavailable
public void onLoaderReset(Loader<Cursor> loader) {
    // This is called when the last Cursor provided to onLoadFinished()
    // above is about to be closed. We need to make sure we are no
    // longer using it.
    mAdapter.swapCursor(null);
}

@Override
public void onListItemClick(ListView l, View v, int position, long id) {
    // Do something when a list item is clicked
}

}

我的logcat：

E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
Process: com.wouterdesigns.a8383, PID: 13242
java.lang.RuntimeException: An error occurred while executing doInBackground()
    at android.os.AsyncTask$3.done(AsyncTask.java:365)
    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
    at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
    at java.util.concurrent.FutureTask.run(FutureTask.java:271)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
    at java.lang.Thread.run(Thread.java:784)
 Caused by: java.lang.SecurityException: Permission Denial: opening provider com.android.providers.contacts.ContactsProvider2 from ProcessRecord{866b18b 13242:com.wouterdesigns.a8383/u0a209} (pid=13242, uid=10209) requires android.permission.READ_CONTACTS or android.permission.WRITE_CONTACTS
    at android.os.Parcel.readException(Parcel.java:1945)
    at android.os.Parcel.readException(Parcel.java:1891)
    at android.app.IActivityManager$Stub$Proxy.getContentProvider(IActivityManager.java:4779)
    at android.app.ActivityThread.acquireProvider(ActivityThread.java:6645)
    at android.app.ContextImpl$ApplicationContentResolver.acquireUnstableProvider(ContextImpl.java:2798)
    at android.content.ContentResolver.acquireUnstableProvider(ContentResolver.java:1820)
    at android.content.ContentResolver.query(ContentResolver.java:750)
    at android.content.ContentResolver.query(ContentResolver.java:716)
    at android.content.CursorLoader.loadInBackground(CursorLoader.java:64)
    at android.content.CursorLoader.loadInBackground(CursorLoader.java:54)
    at android.content.AsyncTaskLoader.onLoadInBackground(AsyncTaskLoader.java:315)
    at android.content.AsyncTaskLoader$LoadTask.doInBackground(AsyncTaskLoader.java:69)
    at android.content.AsyncTaskLoader$LoadTask.doInBackground(AsyncTaskLoader.java:64)
    at android.os.AsyncTask$2.call(AsyncTask.java:345)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636) 
    at java.lang.Thread.run(Thread.java:784)

1 个答案:

答案 0 :(得分：0)

如果您要针对Android M（targetSdkVersion 23）进行测试，则必须在运行时请求权限。例如，这些问题已经回答了这个问题：

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