Android Studio标准ListView点击按钮崩溃问题求助

Hey there! Let's figure out why your app crashes when navigating to the ListViewLoader activity. Based on your code and the partial Logcat output, the most likely culprit is missing permissions for accessing device contacts—here's how to fix it step by step:

1. Add Contacts Permission to Manifest #

First, you need to declare the READ_CONTACTS permission in your AndroidManifest.xml file. Add this line inside the root <manifest> tag (before the <application> tag):

<uses-permission android:name="android.permission.READ_CONTACTS" />

2. Request Runtime Permission (Android 6.0+) #

Android 6.0 (API level 23) and above require apps to request dangerous permissions like contact access at runtime, not just in the manifest. Update your ListViewLoader code to handle this:

Update the onCreate Method #

Modify the onCreate method to check for permission before initializing the loader:

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

    // Keep your existing progress bar setup code here
    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);
    ViewGroup root = (ViewGroup) findViewById(android.R.id.content);
    root.addView(progressBar);

    // Keep your existing cursor adapter setup code here
    String[] fromColumns = {ContactsContract.Data.DISPLAY_NAME};
    int[] toViews = {android.R.id.text1};
    mAdapter = new SimpleCursorAdapter(this, android.R.layout.simple_list_item_1, null, fromColumns, toViews, 0);
    setListAdapter(mAdapter);

    // Check and request READ_CONTACTS permission
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_CONTACTS)
            != PackageManager.PERMISSION_GRANTED) {
        // Request permission from user
        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.READ_CONTACTS},
                100); // Request code can be any integer
    } else {
        // Permission already granted, initialize loader
        getLoaderManager().initLoader(0, null, this);
    }
}

Add Permission Result Handler #

Add this method to your ListViewLoader class to handle the user's permission choice:

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if (requestCode == 100) {
        if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            // Permission approved, start loading contacts
            getLoaderManager().initLoader(0, null, this);
        } else {
            // Permission denied—notify user and go back to MainActivity
            Toast.makeText(this, "Cannot load contacts without permission", Toast.LENGTH_SHORT).show();
            finish();
        }
    }
}

Import Required Packages #

Don't forget to add these imports at the top of ListViewLoader.java:

import android.Manifest;
import android.content.pm.PackageManager;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.widget.Toast;

3. Verify Logcat for Additional Issues #

If the crash still happens after adding permissions, check the full Logcat output (your snippet cuts off). Common secondary issues could include:

• Incorrect URI or projection in the CursorLoader (your current PROJECTION uses ContactsContract.Data._ID and DISPLAY_NAME, which is valid, but double-check the URI)
• Issues with the SimpleCursorAdapter configuration

Why This Works #

The crash occurs because your app tries to access contact data without proper permission. Android runs the CursorLoader in a background thread (hence the AsyncTask #1 error), and when it hits a permission denial, it throws an unhandled exception. By requesting the permission upfront, you let the user grant access before the loader tries to fetch data.

内容的提问来源于stack exchange，提问作者Wouter