在尝试加载以下 Activity 时，我遇到了 NullPoint 异常，我尝试解决这些问题，但我的尝试没有成功。
简而言之，有两个 Activity - 一个 Activity 填充数组列表，单击数组列表中的某个项目后，用户将进入第二个 Activity 页面(此页面)，该页面填充有关该项目的更多信息。我的问题已在第二个 Activity 中通过 JSON 填充图像时得到解决。
下面是 logcat 消息:
08-28 23:35:21.478: E/AndroidRuntime(5085): FATAL EXCEPTION: main
08-28 23:35:21.478: E/AndroidRuntime(5085): Process: com.dooba.beta, PID: 5085
08-28 23:35:21.478: E/AndroidRuntime(5085): java.lang.NullPointerException
08-28 23:35:21.478: E/AndroidRuntime(5085): at com.android.volley.toolbox.ImageLoader.get(ImageLoader.java:233)
08-28 23:35:21.478: E/AndroidRuntime(5085): at com.android.volley.toolbox.ImageLoader.get(ImageLoader.java:171)
08-28 23:35:21.478: E/AndroidRuntime(5085): at com.android.volley.toolbox.NetworkImageView.loadImageIfNecessary(NetworkImageView.java:140)
08-28 23:35:21.478: E/AndroidRuntime(5085): at com.android.volley.toolbox.NetworkImageView.onLayout(NetworkImageView.java:180)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.View.layout(View.java:14817)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java:1660)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.widget.LinearLayout.onLayout(LinearLayout.java:1436)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.View.layout(View.java:14817)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.ViewGroup.layout(ViewGroup.java:4631)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.widget.HorizontalScrollView.onLayout(HorizontalScrollView.java:1474)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.View.layout(View.java:14817)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.ViewGroup.layout(ViewGroup.java:4631)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1055)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.View.layout(View.java:14817)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.ViewGroup.layout(ViewGroup.java:4631)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.View.layout(View.java:14817)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.ViewGroup.layout(ViewGroup.java:4631)
08-28 23:35:21.478: E/AndroidRuntime(5085): at com.android.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:374)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.View.layout(View.java:14817)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.ViewGroup.layout(ViewGroup.java:4631)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.View.layout(View.java:14817)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.ViewGroup.layout(ViewGroup.java:4631)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1987)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1744)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.Choreographer.doCallbacks(Choreographer.java:574)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.Choreographer.doFrame(Choreographer.java:544)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.os.Handler.handleCallback(Handler.java:733)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.os.Handler.dispatchMessage(Handler.java:95)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.os.Looper.loop(Looper.java:136)
08-28 23:35:21.478: E/AndroidRuntime(5085): at android.app.ActivityThread.main(ActivityThread.java:5017)
08-28 23:35:21.478: E/AndroidRuntime(5085): at java.lang.reflect.Method.invokeNative(Native Method)
08-28 23:35:21.478: E/AndroidRuntime(5085): at java.lang.reflect.Method.invoke(Method.java:515)
08-28 23:35:21.478: E/AndroidRuntime(5085): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
08-28 23:35:21.478: E/AndroidRuntime(5085): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
08-28 23:35:21.478: E/AndroidRuntime(5085): at dalvik.system.NativeStart.main(Native Method)
第一个 Activity 代码
public class CasualEventsActivity extends Activity {
private static final String URL_WEB_SERVICE = "http://dooba.ca/analytics/casual.php";
private GridView gv;
private ArrayList<Events_List> container;
private ArrayList<Events_List> items;
public Uri list_item_bac;
public String list_item_name;
public String list_item_description;
public String list_item_location;
public String single_list_item_description;
public String list_item_price;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.events_list_layout);
gv = (GridView) findViewById(R.id.gridview);
container = new ArrayList<Events_List>();
//download JSON
listDownload();
GridView s = (GridView) findViewById(R.id.gridview);
s.setOnItemClickListener(new OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(CasualEventsActivity.this,CasualEventsSingleItemActivity.class);
intent.putExtra("list_item_name", container.get(position).getList_item_title());
intent.putExtra("list_item_location", container.get(position).getList_item_location());
intent.putExtra("single_list_item_description", container.get(position).getSingle_list_item_description());
startActivity(intent); //start Activity
}
});
}
public void listDownload(){
RequestQueue volley = Volley.newRequestQueue(this);
JsonObjectRequest json = new JsonObjectRequest(Method.GET, URL_WEB_SERVICE, null, ResponseListener(), ErrorListener());
volley.add(json);
}
private Response.Listener<JSONObject> ResponseListener() {
return new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
try {
//your JSON Array
JSONArray array = response.getJSONArray("list_item");
for(int i = 0; i < array.length(); i++){
container.add(convertirAnuncio(array.getJSONObject(i)));
}
} catch (JSONException e) {
e.printStackTrace();
}
gv.setAdapter(new AdapterEvents(getApplicationContext(),container));
}
};
};
private Response.ErrorListener ErrorListener() {
return new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) { }
};
}
//object JSON
private final Events_List convertirAnuncio(JSONObject obj) throws JSONException {
long id = obj.getLong("id"); //id
String list_item_name = obj.getString("list_item_name");
String list_item_location = obj.getString("list_item_location");
String list_item_description = obj.getString("list_item_description");
String single_list_item_description = obj.getString("single_list_item_description");
Uri uri = Uri.parse(obj.getString("list_item_bac"));
return new Events_List(id, list_item_location, single_list_item_description,list_item_name,list_item_description,list_item_price, uri);
}
}
第二个 Activity 代码
public class CasualEventsSingleItemActivity extends Activity {
// Declare Variables
String list_item_name;
String list_item_description;
String list_item_price;
String list_item_location;
String single_list_item_description;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_events_single_item);
RequestQueue mRequestQueue = null;
ImageLoader mImageLoader = new ImageLoader(mRequestQueue,
new ImageLoader.ImageCache() {
private final LruCache<String, Bitmap>
cache = new LruCache<String, Bitmap>(20);
@Override
public Bitmap getBitmap(String url) {
return cache.get(url);
}
@Override
public void putBitmap(String url, Bitmap bitmap) {
cache.put(url, bitmap);
}
});
Intent i = getIntent();
list_item_name = i.getStringExtra("list_item_name");
list_item_location = i.getStringExtra("list_item_location");
single_list_item_description = i.getStringExtra("single_list_item_description");
TextView txtname = (TextView) findViewById(R.id.name);
TextView txtlocation = (TextView) findViewById(R.id.location);
TextView txtsdescription = (TextView) findViewById(R.id.sdescription);
NetworkImageView hsvimage1 = (NetworkImageView) findViewById(R.id.hsvimage1);
NetworkImageView hsvimage2 = (NetworkImageView) findViewById(R.id.hsvimage2);
NetworkImageView hsvimage3 = (NetworkImageView) findViewById(R.id.hsvimage3);
// Get image URLs from your previous network request...
// I could not determine where this is stored from code in your question.
String url1 = "I would want to populate the list_bac JSON string that links to a image URL"; // e.g. http://example.com/images/image1.png
String url2 = "I would want to populate the list_bac JSON string that links to a image URL";
String url3 = "I would want to populate the list_bac JSON string that links to a image URL";
// Set the URL of the image that should be loaded into this view, and
// specify the ImageLoader that will be used to make the request.
hsvimage1.setImageUrl(url1, mImageLoader);
hsvimage2.setImageUrl(url2, mImageLoader);
hsvimage3.setImageUrl(url3, mImageLoader);
// Set results to the TextViews
txtname.setText(list_item_name);
txtlocation.setText(list_item_location);
txtsdescription.setText(single_list_item_description);
Button mConfirm2 = (Button)findViewById(R.id.bConfirm2);
mConfirm2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ParseUser currentUser = ParseUser.getCurrentUser();
// Create the class and the columns
currentUser.saveInBackground();
currentUser.put("ActivityName", list_item_name);
currentUser.saveInBackground(new SaveCallback() {
@Override
public void done(ParseException e) {
setProgressBarIndeterminateVisibility(false);
if (e == null) {
// Success!
Intent intent = new Intent(CasualEventsSingleItemActivity.this, usermatch.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
}
else {
AlertDialog.Builder builder = new AlertDialog.Builder(CasualEventsSingleItemActivity.this);
builder.setMessage(e.getMessage())
.setTitle(R.string.signup_error_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
}
});
//CasualEventsSingleItemActivity.this.startActivity(new Intent(CasualEventsSingleItemActivity.this, MatchingActivity.class));
}
});
}
第二个 Activity 布局
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/blue_bac3"
android:gravity="center"
android:orientation="vertical" >
<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_marginLeft="15dp"
android:layout_marginTop="10dp"
android:layout_marginRight="15dp"
android:alpha="0.9"
android:paddingBottom="3dp"
android:shadowColor="#000000"
android:shadowDx="3"
android:shadowDy="3"
android:shadowRadius="0.01"
android:textColor="#82CAFF"
android:textSize="24sp" />
<TextView
android:id="@+id/location"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/name"
android:layout_centerHorizontal="true"
android:layout_marginLeft="15dp"
android:layout_marginRight="15dp"
android:alpha="0.8"
android:paddingBottom="5dp"
android:shadowColor="#000000"
android:shadowDx="3"
android:shadowDy="3"
android:shadowRadius="0.01"
android:textAlignment="center"
android:textColor="#f2f2f2"
android:textSize="16sp" />
<ImageView
android:id="@+id/dividertop"
android:layout_width="370dp"
android:layout_centerHorizontal="true"
android:layout_height="wrap_content"
android:layout_below="@+id/location"
android:alpha="0.6"
android:background="@drawable/divider11"
android:paddingBottom="3dp" />
<ImageView
android:id="@+id/dividerbottom"
android:layout_width="370dp"
android:layout_centerHorizontal="true"
android:layout_height="wrap_content"
android:layout_below="@+id/vsvdescription"
android:alpha="0.6"
android:background="@drawable/divider11"
android:paddingBottom="3dp" />
<ImageView
android:id="@+id/image_head"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:background="#000000"
android:padding="1dp" />
<HorizontalScrollView
android:id="@+id/isgallery"
android:layout_width="370dp"
android:layout_height="90dp"
android:layout_centerHorizontal="true"
android:layout_below="@+id/dividerbottom"
android:layout_marginTop="8dp"
>
<LinearLayout
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<com.android.volley.toolbox.NetworkImageView
android:id="@+id/hsvimage1"
android:layout_width="148dp"
android:layout_height="90dp"
android:layout_marginRight="6dp"
android:layout_alignParentRight="true"
android:background="#fff"
android:padding="1dp" />
<com.android.volley.toolbox.NetworkImageView
android:id="@+id/hsvimage2"
android:layout_width="148dp"
android:layout_height="90dp"
android:layout_marginRight="6dp"
android:layout_alignParentRight="true"
android:background="#000000"
android:padding="1dp" />
<com.android.volley.toolbox.NetworkImageView
android:id="@+id/hsvimage3"
android:layout_width="148dp"
android:layout_height="90dp"
android:layout_marginRight="6dp"
android:layout_alignParentRight="true"
android:background="#CCC"
android:padding="1dp" />
<com.android.volley.toolbox.NetworkImageView
android:id="@+id/hsvimage4"
android:layout_width="148dp"
android:layout_height="90dp"
android:layout_alignParentRight="true"
android:background="#000000"
android:padding="1dp" />
</LinearLayout>
</HorizontalScrollView>
<Button
android:id="@+id/bConfirm2"
android:layout_width="90dp"
android:layout_height="50dp"
android:layout_below="@+id/isgallery"
android:layout_centerHorizontal="true"
android:alpha="0.7"
android:layout_marginTop="10dp"
android:background="@drawable/gray_bac"
android:text="Confirm"
android:textColor="#2B3856"
android:textStyle="bold" />
<ScrollView
android:id="@+id/vsvdescription"
android:layout_width="370dp"
android:layout_height="250dp"
android:layout_marginTop="7dp"
android:layout_marginBottom="7dp"
android:padding="5dp"
android:layout_centerHorizontal="true"
android:layout_below="@+id/dividertop"
>
<RelativeLayout
android:orientation="vertical"
android:gravity="center"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<TextView
android:id="@+id/sdescription"
android:layout_width="370dp"
android:layout_height="250dp"
android:gravity="center"
android:alpha="0.65"
android:textColor="#ffffff"
android:textSize="18sp" />
</RelativeLayout>
</ScrollView>
</RelativeLayout>
提前致谢
更新
public class CasualEventsSingleItemActivity extends Activity {
// Declare Variables
String list_item_name;
String list_item_description;
String list_item_price;
String list_item_location;
String single_list_item_description;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_events_single_item);
ImageLoader mImageLoader = new ImageLoader(Volley.newRequestQueue(this),
new ImageLoader.ImageCache() {
private final LruCache<String, Bitmap>
cache = new LruCache<String, Bitmap>(20);
@Override
public Bitmap getBitmap(String url) {
return cache.get(url);
}
@Override
public void putBitmap(String url, Bitmap bitmap) {
cache.put(url, bitmap);
}
});
Intent i = getIntent();
list_item_name = i.getStringExtra("list_item_name");
list_item_location = i.getStringExtra("list_item_location");
single_list_item_description = i.getStringExtra("single_list_item_description");
TextView txtname = (TextView) findViewById(R.id.name);
TextView txtlocation = (TextView) findViewById(R.id.location);
TextView txtsdescription = (TextView) findViewById(R.id.sdescription);
NetworkImageView hsvimage1 = (NetworkImageView) findViewById(R.id.hsvimage1);
NetworkImageView hsvimage2 = (NetworkImageView) findViewById(R.id.hsvimage2);
NetworkImageView hsvimage3 = (NetworkImageView) findViewById(R.id.hsvimage3);
// Get image URLs from your previous network request...
// I could not determine where this is stored from code in your question.
String url1 = "list_item_bac"; // e.g. http://example.com/images/image1.png
String url2 = "list_item_bac";
String url3 = "list_item_bac ";
// Set the URL of the image that should be loaded into this view, and
// specify the ImageLoader that will be used to make the request.
hsvimage1.setImageUrl(url1, mImageLoader);
hsvimage2.setImageUrl(url2, mImageLoader);
hsvimage3.setImageUrl(url3, mImageLoader);
// Set results to the TextViews
txtname.setText(list_item_name);
txtlocation.setText(list_item_location);
txtsdescription.setText(single_list_item_description);
Button mConfirm2 = (Button)findViewById(R.id.bConfirm2);
mConfirm2.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ParseUser currentUser = ParseUser.getCurrentUser();
// Create the class and the columns
currentUser.saveInBackground();
currentUser.put("ActivityName", list_item_name);
currentUser.saveInBackground(new SaveCallback() {
@Override
public void done(ParseException e) {
setProgressBarIndeterminateVisibility(false);
if (e == null) {
// Success!
Intent intent = new Intent(CasualEventsSingleItemActivity.this, usermatch.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
}
else {
AlertDialog.Builder builder = new AlertDialog.Builder(CasualEventsSingleItemActivity.this);
builder.setMessage(e.getMessage())
.setTitle(R.string.signup_error_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
}
});
//CasualEventsSingleItemActivity.this.startActivity(new Intent(CasualEventsSingleItemActivity.this, MatchingActivity.class));
}
});
}
}
最佳答案
这是您获取 NPE 的代码
* Constructs a new ImageLoader.
* @param queue The RequestQueue to use for making image requests.
* @param imageCache The cache to use as an L1 cache.
*/
public ImageLoader(RequestQueue queue, ImageCache imageCache) {
mRequestQueue = queue;
mCache = imageCache;
}
那么为什么要为第一个参数传递 null 呢？
Also as per the code
/**
* Helper that handles loading and caching images from remote URLs.
*
* The simple way to use this class is to call {@link ImageLoader#get(String, ImageListener)}
* and to pass in the default image listener provided by
* {@link ImageLoader#getImageListener(ImageView, int, int)}. Note that all function calls to
* this class must be made from the main thead, and all responses will be delivered to the main
* thread as well.
*/
所以我会听取他们的建议并使用ImageLoader.get(String requestUrl，最终的ImageListener监听器)
关于java - 空点异常 - ImageLoader，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25560013/