应用程序的主要目的是下载和显示图像，但是当我尝试启动应用程序时它崩溃了。
这是我的代码。
private DownloadImageTask task;
protected void onCreate(Bundle savedInstanceState) {
task = new DownloadImageTask();
task.onPostExecute(task.doInBackground("http://parkcinema.az/uploads/structures/movies/images/xickok_poster1_resized.jpg"));
}
private class DownloadImageTask extends AsyncTask <String, Void, Bitmap> {
protected Bitmap doInBackground(String... urls) {
String urldisplay = urls[0];
Bitmap mIcon11 = null;
try {
InputStream in = new java.net.URL(urldisplay).openStream();
mIcon11 = BitmapFactory.decodeStream(in);
} catch (Exception e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return mIcon11;
}
protected void onPostExecute(Bitmap result) {
ImageView img = (ImageView) findViewById(R.id.imageView1);
img.setImageBitmap(result);
}
}
这是 LogCat：
02-24 11:04:56.814: E/Trace(957): error opening trace file: No such file or directory (2)
02-24 11:04:57.384: D/AndroidRuntime(957): Shutting down VM
02-24 11:04:57.384: W/dalvikvm(957): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
02-24 11:04:57.404: E/AndroidRuntime(957): FATAL EXCEPTION: main
02-24 11:04:57.404: E/AndroidRuntime(957): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.bakumovies/com.example.bakumovies.MainActivity}: java.lang.NullPointerException: println needs a message
02-24 11:04:57.404: E/AndroidRuntime(957): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
02-24 11:04:57.404: E/AndroidRuntime(957): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
02-24 11:04:57.404: E/AndroidRuntime(957): at android.app.ActivityThread.access$600(ActivityThread.java:130)
02-24 11:04:57.404: E/AndroidRuntime(957): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
02-24 11:04:57.404: E/AndroidRuntime(957): at android.os.Handler.dispatchMessage(Handler.java:99)
02-24 11:04:57.404: E/AndroidRuntime(957): at android.os.Looper.loop(Looper.java:137)
02-24 11:04:57.404: E/AndroidRuntime(957): at android.app.ActivityThread.main(ActivityThread.java:4745)
02-24 11:04:57.404: E/AndroidRuntime(957): at java.lang.reflect.Method.invokeNative(Native Method)
02-24 11:04:57.404: E/AndroidRuntime(957): at java.lang.reflect.Method.invoke(Method.java:511)
02-24 11:04:57.404: E/AndroidRuntime(957): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
02-24 11:04:57.404: E/AndroidRuntime(957): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-24 11:04:57.404: E/AndroidRuntime(957): at dalvik.system.NativeStart.main(Native Method)
02-24 11:04:57.404: E/AndroidRuntime(957): Caused by: java.lang.NullPointerException: println needs a message
02-24 11:04:57.404: E/AndroidRuntime(957): at android.util.Log.println_native(Native Method)
02-24 11:04:57.404: E/AndroidRuntime(957): at android.util.Log.e(Log.java:231)
02-24 11:04:57.404: E/AndroidRuntime(957): at com.example.bakumovies.MainActivity$DownloadImageTask.doInBackground(MainActivity.java:49)
02-24 11:04:57.404: E/AndroidRuntime(957): at com.example.bakumovies.MainActivity.onCreate(MainActivity.java:27)
02-24 11:04:57.404: E/AndroidRuntime(957): at android.app.Activity.performCreate(Activity.java:5008)
02-24 11:04:57.404: E/AndroidRuntime(957): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
02-24 11:04:57.404: E/AndroidRuntime(957): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
02-24 11:04:57.404: E/AndroidRuntime(957): ... 11 more
这是 .xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_centerVertical="true"
android:layout_marginLeft="144dp" />
</RelativeLayout>
我不明白为什么它会崩溃。在新线程中启动图像下载，创建 imageview 对象。我对此完全困惑。
任何帮助将不胜感激。
NPE（空指针异常）的原因
Log.e("错误", e.getMessage()); //e.getMessage() 为 NULL，因此它给出 NPE。
protected void onCreate(Bundle savedInstanceState)
task = new DownloadImageTask().execute("http://parkcinema.az/uploads/structures/movies/images/xickok_poster1_resized.jpg");
}
protected Bitmap doInBackground(String... urls) {
String urldisplay = urls[0];
Bitmap mIcon11 = null;
try {
mIcon11 = BitmapFactory.decodeStream(new URL(urldisplay).openConnection().getInputStream());
}
catch (Exception e) {
e.printStackTrace();
}
return mIcon11;
}
在AndroidManifest.xml中添加此权限，因为您正在进行互联网操作。
<uses-permission android:name="android.permission.INTERNET" />
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