我按照教程列出了所有已安装的软件包＆＃34;应用程序＆＃34;在GridView布局中。到目前为止，这导致了致命的错误。我已经尝试了许多其他的代码变体，但也收到了相同的错误消息。我很抱歉，如果问题看起来太明显，或者我犯了一个非常愚蠢的错误，因为我刚刚在1周前启动Android并且无法找出问题的根源。任何帮助都非常感谢。
public class Launcher extends FragmentActivity {
DrawerAdapter drawerAdapterObject;
GridView drawerGrid;
class Package {
Drawable icon;
String name;
String label;
}
Package[] packs;
PackageManager pm;
ViewPager viewpager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_launcher);
drawerGrid = (GridView) findViewById(R.id.content);
pm=getPackageManager();
set_packs();
drawerAdapterObject = new DrawerAdapter(this, packs);
drawerGrid.setAdapter(drawerAdapterObject);
viewpager = (ViewPager) findViewById(R.id.pager);
PagerAdapter adapter = new PagerAdapter(getSupportFragmentManager());
viewpager.setAdapter(adapter);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
Window w = getWindow();
w.setFlags(WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS, WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS);
}
}
public void set_packs() {
final Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);
List<ResolveInfo> packsList = pm.queryIntentActivities(mainIntent, 0);
packs = new Package[packsList.size()];
for(int I=0;I<packsList.size();I++){
packs[I]= new Package();
packs[I].icon=packsList.get(I).loadIcon(pm);
packs[I].name=packsList.get(I).activityInfo.packageName;
packs[I].label=packsList.get(I).loadLabel(pm).toString();
}
}
}
public class DrawerAdapter extends BaseAdapter {
Context mContext;
Launcher.Package[] packsForAdapter;
public DrawerAdapter (Context c, Launcher.Package packs[]) {
mContext =c;
packsForAdapter = packs;
}
@Override
public int getCount() {
return packsForAdapter.length;
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int pos, View convertView, ViewGroup parent) {
ImageView imageView = new ImageView(mContext);
imageView.setImageDrawable(packsForAdapter[pos].icon);
imageView.setLayoutParams(new GridView.LayoutParams(65, 65));
imageView.setPadding(3,3,3,3);
return imageView;
}
}
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_apps"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffffff"
tools:context="com.visualartsinternational.www.artui.Launcher">
<GridView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/content"
android:columnWidth="90dp"
android:numColumns="auto_fit"
android:verticalSpacing="50dp"
android:horizontalSpacing="50dp"
android:stretchMode="columnWidth"
android:gravity="center"/>
</RelativeLayout>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_launcher"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
tools:context="com.visualartsinternational.www.artui.Launcher">
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</android.support.v4.view.ViewPager>
</RelativeLayout>
01-07 15:10:28.023 14259-14259/? I/art: Not late-enabling -Xcheck:jni (already on)
01-07 15:10:28.023 14259-14259/? W/art: Unexpected CPU variant for X86 using defaults: x86
01-07 15:10:28.039 14259-14265/? I/art: Debugger is no longer active
01-07 15:10:28.040 14259-14265/? I/art: Starting a blocking GC Instrumentation
01-07 15:10:28.266 14259-14259/? W/ActivityThread: Application com.visualartsinternational.www.artui is waiting for the debugger on port 8100...
01-07 15:10:28.267 14259-14259/? I/System.out: Sending WAIT chunk
01-07 15:10:29.249 14259-14265/com.visualartsinternational.www.artui I/art: Debugger is active
01-07 15:10:29.272 14259-14259/com.visualartsinternational.www.artui I/System.out: Debugger has connected
01-07 15:10:29.272 14259-14259/com.visualartsinternational.www.artui I/System.out: waiting for debugger to settle...
01-07 15:10:29.474 14259-14259/com.visualartsinternational.www.artui I/System.out: waiting for debugger to settle...
01-07 15:10:29.674 14259-14259/com.visualartsinternational.www.artui I/System.out: waiting for debugger to settle...
01-07 15:10:29.876 14259-14259/com.visualartsinternational.www.artui I/System.out: waiting for debugger to settle...
01-07 15:10:30.078 14259-14259/com.visualartsinternational.www.artui I/System.out: waiting for debugger to settle...
01-07 15:10:30.279 14259-14259/com.visualartsinternational.www.artui I/System.out: waiting for debugger to settle...
01-07 15:10:30.480 14259-14259/com.visualartsinternational.www.artui I/System.out: waiting for debugger to settle...
01-07 15:10:30.681 14259-14259/com.visualartsinternational.www.artui I/System.out: waiting for debugger to settle...
01-07 15:10:30.882 14259-14259/com.visualartsinternational.www.artui I/System.out: debugger has settled (1463)
01-07 15:10:30.886 14259-14259/com.visualartsinternational.www.artui W/System: ClassLoader referenced unknown path: /data/app/com.visualartsinternational.www.artui-1/lib/x86
01-07 15:10:30.894 14259-14259/com.visualartsinternational.www.artui I/InstantRun: Instant Run Runtime started. Android package is com.visualartsinternational.www.artui, real application class is null.
01-07 15:10:31.061 14259-14259/com.visualartsinternational.www.artui W/System: ClassLoader referenced unknown path: /data/app/com.visualartsinternational.www.artui-1/lib/x86
01-07 15:10:31.245 14259-14259/com.visualartsinternational.www.artui W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
01-07 15:10:31.467 14259-14263/com.visualartsinternational.www.artui I/art: Do partial code cache collection, code=30KB, data=26KB
01-07 15:10:31.470 14259-14263/com.visualartsinternational.www.artui I/art: After code cache collection, code=28KB, data=27KB
01-07 15:10:31.470 14259-14263/com.visualartsinternational.www.artui I/art: Increasing code cache capacity to 128KB
01-07 15:10:31.509 14259-14259/com.visualartsinternational.www.artui D/AndroidRuntime: Shutting down VM
01-07 15:10:31.510 14259-14259/com.visualartsinternational.www.artui E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.visualartsinternational.www.artui, PID: 14259
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.visualartsinternational.www.artui/com.visualartsinternational.www.artui.Launcher}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.GridView.setAdapter(android.widget.ListAdapter)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.GridView.setAdapter(android.widget.ListAdapter)' on a null object reference
at com.visualartsinternational.www.artui.Launcher.onCreate(Launcher.java:36)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
答案 0 :(得分：1)
活动使用的布局与activity_apps.xml不同
你正在做setContentView(R.layout.activity_launcher)
将其替换为setContentView(R.layout.activity_apps)或将GridView添加到activity_launcher.xml