Java 截击图像加载程序库错误EXCEPTION
大家好,在本教程之后,我正在尝试使用截图提要创建自定义视图列表: 但是我的图像加载器出了一个错误,我无法掌握它的窍门,我希望有人能告诉我问题出在哪里,我首先应该如何解决:) 提前谢谢 这就是错误:Java 截击图像加载程序库错误EXCEPTION,java,android,android-volley,Java,Android,Android Volley,大家好,在本教程之后,我正在尝试使用截图提要创建自定义视图列表: 但是我的图像加载器出了一个错误,我无法掌握它的窍门,我希望有人能告诉我问题出在哪里,我首先应该如何解决:) 提前谢谢 这就是错误: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.asro9.customfeed/com.example.asro9.customfeed.MainActivity}: java.lang.N
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.asro9.customfeed/com.example.asro9.customfeed.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at Adapter.FeedListAdapter.<init>(FeedListAdapter.java:33)
at com.example.asro9.customfeed.MainActivity.onCreate(MainActivity.java:50)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
MainActivity.java
package com.example.asro9.customfeed;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.view.Menu;
import android.widget.ListView;
import org.json.JSONException;
import java.util.ArrayList;
import java.util.List;
import Adapter.FeedListAdapter;
import CustomFeed.AppController;
import Data.FeedItem;
import com.android.volley.Cache;
import com.android.volley.Cache.Entry;
import com.android.volley.Request.Method;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.android.volley.toolbox.JsonObjectRequest;
import java.io.UnsupportedEncodingException;
import org.json.JSONArray;
import org.json.JSONObject;
public class MainActivity extends Activity {
private static final String TAG = MainActivity.class.getSimpleName();
private ListView listView;
private FeedListAdapter listAdapter;
private List<FeedItem> feedItems;
private String URL_FEED = "http://api.androidhive.info/feed/feed.json";
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.list);
feedItems = new ArrayList<FeedItem>();
listAdapter = new FeedListAdapter(this, feedItems);
listView.setAdapter(listAdapter);
// These two lines not needed,
// just to get the look of facebook (changing background color & hiding the icon)
getActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#3b5998")));
getActionBar().setIcon(
new ColorDrawable(getResources().getColor(android.R.color.transparent)));
// We first check for cached request
Cache cache = AppController.getInstance().getRequestQueue().getCache();
Entry entry = cache.get(URL_FEED);
if (entry != null) {
// fetch the data from cache
try {
String data = new String(entry.data, "UTF-8");
try {
parseJsonFeed(new JSONObject(data));
} catch (JSONException e) {
e.printStackTrace();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
} else {
// making fresh volley request and getting json
JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
URL_FEED, null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
VolleyLog.d(TAG, "Response: " + response.toString());
if (response != null) {
parseJsonFeed(response);
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
}
});
// Adding request to volley request queue
AppController.getInstance().addToRequestQueue(jsonReq);
}
}
/**
* Parsing json reponse and passing the data to feed view list adapter
* */
private void parseJsonFeed(JSONObject response) {
try {
JSONArray feedArray = response.getJSONArray("feed");
for (int i = 0; i < feedArray.length(); i++) {
JSONObject feedObj = (JSONObject) feedArray.get(i);
FeedItem item = new FeedItem();
item.setId(feedObj.getInt("id"));
item.setName(feedObj.getString("name"));
// Image might be null sometimes
String image = feedObj.isNull("image") ? null : feedObj
.getString("image");
item.setImge(image);
item.setStatus(feedObj.getString("status"));
item.setProfilePic(feedObj.getString("profilePic"));
item.setTimeStamp(feedObj.getString("timeStamp"));
// url might be null sometimes
String feedUrl = feedObj.isNull("url") ? null : feedObj
.getString("url");
item.setUrl(feedUrl);
feedItems.add(item);
}
// notify data changes to list adapater
listAdapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
}
截击缓存
lRubitMacache:
package Volly;
import android.graphics.Bitmap;
import android.support.v4.util.LruCache;
import com.android.volley.toolbox.ImageLoader.ImageCache;
/**
* Created by asro9 on 3/7/2016.
*/
public class LruBitmapCache extends LruCache<String, Bitmap> implements
ImageCache {
public static int getDefaultLruCacheSize() {
final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);
final int cacheSize = maxMemory / 8;
return cacheSize;
}
public LruBitmapCache() {
this(getDefaultLruCacheSize());
}
public LruBitmapCache(int sizeInKiloBytes) {
super(sizeInKiloBytes);
}
@Override
protected int sizeOf(String key, Bitmap value) {
return value.getRowBytes() * value.getHeight() / 1024;
}
@Override
public Bitmap getBitmap(String url) {
return get(url);
}
@Override
public void putBitmap(String url, Bitmap bitmap) {
put(url, bitmap);
}
}
Volly打包;
导入android.graphics.Bitmap;
导入android.support.v4.util.LruCache;
导入com.android.volley.toolbox.ImageLoader.ImageCache;
/**
*由asro9于2016年3月7日创建。
*/
公共类LruBitmapCache扩展了LruCache实现
图像缓存{
公共静态int getDefaultLruCacheSize(){
final int maxMemory=(int)(Runtime.getRuntime().maxMemory()/1024);
最终int cacheSize=maxMemory/8;
返回缓存大小;
}
公共LRubitMacache(){
这个(getDefaultLruCacheSize());
}
公共lrubitMacache(int-sizeInKiloBytes){
超级(sizeInKiloBytes);
}
@凌驾
受保护的int-sizeOf(字符串键、位图值){
返回值.getRowBytes()*value.getHeight()/1024;
}
@凌驾
公共位图getBitmap(字符串url){
返回get(url);
}
@凌驾
公共位图(字符串url、位图){
put(url、位图);
}
}
错误是不言自明的,崩溃在这里:
ImageLoader imageLoader = AppController.getInstance().getImageLoader();
getInstance返回null。很抱歉,我是个业余爱好者,我不明白你的意思。请确保你正在初始化应用程序类中的MinInstance变量。在该实例上调用getImageLoader()会抛出一个NPE,因此逻辑结论是MinInstance为null。
package CustomFeed;
import android.app.Application;
import android.text.TextUtils;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.Volley;
import Volly.LruBitmapCache;
/**
* Created by asro9 on 3/9/2016.
*/
public class AppController extends Application {
public static final String TAG = AppController.class.getSimpleName();
private RequestQueue mRequestQueue;
private ImageLoader mImageLoader;
LruBitmapCache mLruBitmapCache;
private static AppController mInstance;
@Override
public void onCreate() {
super.onCreate();
mInstance = this;
}
public static synchronized AppController getInstance() {
return mInstance;
}
public RequestQueue getRequestQueue() {
if (mRequestQueue == null) {
mRequestQueue = Volley.newRequestQueue(getApplicationContext());
}
return mRequestQueue;
}
public ImageLoader getImageLoader() {
getRequestQueue();
if (mImageLoader == null) {
getLruBitmapCache();
mImageLoader = new ImageLoader(this.mRequestQueue, mLruBitmapCache);
}
return this.mImageLoader;
}
public LruBitmapCache getLruBitmapCache() {
if (mLruBitmapCache == null)
mLruBitmapCache = new LruBitmapCache();
return this.mLruBitmapCache;
}
public <T> void addToRequestQueue(Request<T> req, String tag) {
req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
getRequestQueue().add(req);
}
public <T> void addToRequestQueue(Request<T> req) {
req.setTag(TAG);
getRequestQueue().add(req);
}
public void cancelPendingRequests(Object tag) {
if (mRequestQueue != null) {
mRequestQueue.cancelAll(tag);
}
}
}
package Data;
/**
* Created by asro9 on 3/7/2016.
*/
public class FeedItem {
private int id;
private String name, status, image, profilePic, timeStamp, url;
public FeedItem() {
}
public FeedItem(int id, String name, String image, String status,
String profilePic, String timeStamp, String url) {
super();
this.id = id;
this.name = name;
this.image = image;
this.status = status;
this.profilePic = profilePic;
this.timeStamp = timeStamp;
this.url = url;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getImge() {
return image;
}
public void setImge(String image) {
this.image = image;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public String getProfilePic() {
return profilePic;
}
public void setProfilePic(String profilePic) {
this.profilePic = profilePic;
}
public String getTimeStamp() {
return timeStamp;
}
public void setTimeStamp(String timeStamp) {
this.timeStamp = timeStamp;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
}
package Volly;
import android.graphics.Bitmap;
import android.support.v4.util.LruCache;
import com.android.volley.toolbox.ImageLoader.ImageCache;
/**
* Created by asro9 on 3/7/2016.
*/
public class LruBitmapCache extends LruCache<String, Bitmap> implements
ImageCache {
public static int getDefaultLruCacheSize() {
final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);
final int cacheSize = maxMemory / 8;
return cacheSize;
}
public LruBitmapCache() {
this(getDefaultLruCacheSize());
}
public LruBitmapCache(int sizeInKiloBytes) {
super(sizeInKiloBytes);
}
@Override
protected int sizeOf(String key, Bitmap value) {
return value.getRowBytes() * value.getHeight() / 1024;
}
@Override
public Bitmap getBitmap(String url) {
return get(url);
}
@Override
public void putBitmap(String url, Bitmap bitmap) {
put(url, bitmap);
}
}
ImageLoader imageLoader = AppController.getInstance().getImageLoader();