图像Uri错误

Question

我正在创建一个通讯录应用程序，我想从通讯录数据库中获取通讯录图像。 我一直收到此Uri错误。 似乎错误出现在第97行：@ thumb.setImageURI(uri); 。 请协助我做什么。 谢谢。

这是我的AddressBook.java类

package com.rufflez.viewpagerexample;

import android.support.v4.app.ListFragment;
import android.app.LoaderManager.LoaderCallbacks;
import android.content.ContentUris;
import android.content.Context;
import android.content.CursorLoader;
import android.content.Loader;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.Contacts;
import android.provider.ContactsContract;
import android.support.v4.widget.CursorAdapter;
import android.support.v4.widget.SimpleCursorAdapter;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ListView;

public class AddressBook extends ListFragment implements 
LoaderCallbacks<Cursor>{

private CursorAdapter mAdapter;
public ListView listView;
public Cursor cursor;


public static final String[] FROM = { ContactsContract.Contacts.DISPLAY_NAME_PRIMARY, ContactsContract.Contacts.PHOTO_THUMBNAIL_URI };
private static final int[] TO = { R.id.text_name, R.id.contact_thumbnail };

int layout = R.layout.contact_list_item;



// Name should be displayed in the text1 TextView in item layout

private Context context;
public View view;
public static Uri uri;


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

    // delete list if already there (old version)
    if (!(listView == null)){
        listView.setAdapter(null);
    }

    // create adapter once
    context = getActivity();
    int layout = android.R.layout.simple_list_item_1;
    Cursor c = null; // there is no cursor yet
    int flags = 0; // no auto-requery! Loader requeries.

    // put List in adapter
    mAdapter = new SimpleCursorAdapter(context, layout, c, FROM, TO, flags);



} // end onCreate


// columns requested from the database
private static final String[] PROJECTION = {
    ContactsContract.Contacts._ID,
    ContactsContract.Contacts.PHOTO_THUMBNAIL_URI,
    ContactsContract.Contacts.DISPLAY_NAME_PRIMARY,
    ContactsContract.Contacts.HAS_PHONE_NUMBER,
    ContactsContract.Contacts.IN_VISIBLE_GROUP
};

// this goes in the CursorLoader parameter list, it filters
// out only those contacts who have a phone number
private static final String SELECTION = 
        ContactsContract.Contacts.HAS_PHONE_NUMBER + "='1'";

// Empty public constructor, required by the system
public AddressBook() {}

// A UI Fragment must inflate its View (all fragments must override onCreateView)
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // Inflate the fragment layout
    View view =  inflater.inflate(R.layout.contact_list_view,
            container, false);
    listView = (ListView) view.findViewById(R.id.list); 

    // set Contact photo to ImageView
    AddressBook frag = new AddressBook();
    ImageView thumb = (ImageView)view.findViewById(R.id.contact_thumbnail);
    frag.getPhotoUriFromID(ContactsContract.Contacts._ID);
    thumb.setImageURI(uri);
    return view;
}

public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    // and tell loader manager to start loading
//  getLoaderManager().initLoader(0, null, this);

    listView.setAdapter(mAdapter);
    listView.setFastScrollEnabled(true);

}

// a CursorLoader does a query in the background
@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    // load from the "Contacts table"
    Uri contentUri = Contacts.CONTENT_URI;

    // no sub-selection, no sort order, simply every row
    // projection says we want just the _id and the name column
    return new CursorLoader(getActivity(),
            contentUri,
            PROJECTION,
            SELECTION,
            null,
            ContactsContract.Contacts.DISPLAY_NAME
            );
}

private Uri getPhotoUriFromID(String id) {
    try {
        Cursor cur = context.getContentResolver()
                .query(ContactsContract.Data.CONTENT_URI,
                        null,
                        ContactsContract.Data.CONTACT_ID
                        + "="
                        + id
                        + " AND "
                        + ContactsContract.Data.MIMETYPE
                        + "='"
                        + ContactsContract.CommonDataKinds.Photo.CONTENT_ITEM_TYPE
                        + "'", null, null);
        if (cur != null) {
            if (!cur.moveToFirst()) {
                return null; // no photo
            }
        } else {
            return null; // error in cursor process
        }
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
    Uri person = ContentUris.withAppendedId(
            ContactsContract.Contacts.CONTENT_URI, Long.parseLong(id));
    uri = Uri.withAppendedPath(person,
            ContactsContract.Contacts.Photo.CONTENT_DIRECTORY);
    return uri;
}

@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
    // Once cursor is loaded, give it to adapter
    mAdapter.swapCursor(data);
}

@Override
public void onLoaderReset(Loader<Cursor> loader) {
    // Delete the reference to the existing Cursor,
    // so it can recycle it
    mAdapter.swapCursor(null);
}
}

这是contact_list_view.xml

<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/list"
android:layout_width="match_parent"
android:layout_height="match_parent" >

</ListView>

这是我的contact_list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<ImageView
    android:id="@+id/contact_thumbnail"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/ic_launcher" />

<TextView
    android:id="@+id/text_name"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:clickable="true"/>

</LinearLayout>

这是我的Logcat错误

09-03 20:08:15.241: E/AndroidRuntime(5257): java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageURI(android.net.Uri)' on a null object reference
09-03 20:08:15.241: E/AndroidRuntime(5257):     at com.rufflez.viewpagerexample.AddressBook.onCreateView(AddressBook.java:97)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:938)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1115)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1478)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:478)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.view.View.measure(View.java:18580)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:874)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:612)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.view.View.measure(View.java:18580)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5827)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.view.View.measure(View.java:18580)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5827)
09-03 20:08:15.241: E/AndroidRuntime(5257):     at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:447)

Answer 1

您正在尝试设置一个“不存在”的uri ... thumb.setImageURI（uri）; 将始终为null。

我认为缩略图会出现在您的列表视图中，因此...您需要设置：

thumb.setImageURI（uri）; 在您的自定义适配器中。

一旦应用程序加载，您现在执行的方式（在代码中有错误位置的详细信息）正在尝试获取uri，甚至在设置适配器，获取数据等之前……uri始终为null。

Answer 2

您的片段使用contact_list_view.xml布局，该布局仅包含一个ListView 。 第一次(ImageView)view.findViewById(R.id.contact_thumbnail);该列表时，它不包含(ImageView)view.findViewById(R.id.contact_thumbnail); ，因此(ImageView)view.findViewById(R.id.contact_thumbnail); 将返回null，因为您只有一个ListView 。

核心问题是，为ListView填充和填充子视图是适配器的工作。 您不应该尝试从Fragment内引用contact_list_item.xml任何视图。 这些视图不仅完全可能还不存在，这样做还限制了您只能使用列表的一行，而不是用其各自的数据填充每一行。

Answer 3

public static Uri uri; in not initalized（始终为null ）。

Answer 4

我和Uri有问题。 重新创建我的活动时，它将变量Uri的值设置为null。 这个事实使我的应用程序崩溃了，因为它使用它保存了实例。 如何预防呢？ 以某种方式保存Uri变量的值。 进行sqlite，sharedpreferences或bundle或任何其他选择。 并且当重新创建检查时，其值不为null。 如果是真的，则从内存中获取保存的值。 正如我提醒调用Uri.parseString或smth类似。 我认为你有这样的问题。 祝好运！