Question

我正在尝试实现一个在android中使用带有gridview的viewpager片段的avtivity。每个gridview包含八个系统的应用程序图标，片段的数量是动态的。它运作良好，但滑到第三个片段。对不起我的英文。

在应用程序的当前状态中，我得到以下异常：

   V/test_GridAdapter( 1418): The position is 0, com.android.providers.downloads.ui getView
V/test_GridAdapter( 1418): The position is 0, com.android.providers.downloads.ui getView
V/test_GridAdapter( 1418): The position is 0, com.android.providers.downloads.ui getView
V/test_GridAdapter( 1418): The position is 0, com.android.providers.downloads.ui getView
V/test_GridAdapter( 1418): The position is 0, com.android.providers.downloads.ui getView
V/test_GridAdapter( 1418): The position is 1, com.android.quicksearchbox getView
V/test_GridAdapter( 1418): The position is 2, com.rockchip.gamecontrolsetting getView
V/test_GridAdapter( 1418): The position is 3, com.android.apkinstaller getView
V/test_GridAdapter( 1418): The position is 4, com.android.rockchip getView
V/test_GridAdapter( 1418): The position is 5, com.android.speechrecorder getView
V/test_GridAdapter( 1418): The position is 6, com.android.videoeditor getView
V/test_GridAdapter( 1418): The position is 7, com.rockchip.wfd getView
V/test_GridAdapter( 1418): The position is 0, com.rockchip.mediacenter getView
V/test_GridAdapter( 1418): The position is 0, com.rockchip.mediacenter getView
V/test_GridAdapter( 1418): The position is 0, com.rockchip.mediacenter getView
V/test_GridAdapter( 1418): The position is 0, com.rockchip.mediacenter getView
V/test_GridAdapter( 1418): The position is 0, com.rockchip.mediacenter getView
D/AndroidRuntime( 1418): Shutting down VM
W/dalvikvm( 1418): threadid=1: thread exiting with uncaught exception (group=0x41c79300)
E/AndroidRuntime( 1418): FATAL EXCEPTION: main
E/AndroidRuntime( 1418): Process: com.example.zhengjy.ljlauncher, PID: 1418
E/AndroidRuntime( 1418): java.lang.NullPointerException
E/AndroidRuntime( 1418):    at com.example.zhengjy.ljlauncher.GridAdapter.getView(GridAdapter.java:95)
E/AndroidRuntime( 1418):    at android.widget.AbsListView.obtainView(AbsListView.java:2263)
E/AndroidRuntime( 1418):    at android.widget.GridView.makeAndAddView(GridView.java:1345)
E/AndroidRuntime( 1418):    at android.widget.GridView.makeRow(GridView.java:345)
E/AndroidRuntime( 1418):    at android.widget.GridView.fillDown(GridView.java:287)
E/AndroidRuntime( 1418):    at android.widget.GridView.fillFromTop(GridView.java:421)
E/AndroidRuntime( 1418):    at android.widget.GridView.layoutChildren(GridView.java:1233)
E/AndroidRuntime( 1418):    at android.widget.AbsListView.onLayout(AbsListView.java:2091)
E/AndroidRuntime( 1418):    at android.view.View.layout(View.java:14838)
E/AndroidRuntime( 1418):    at android.view.ViewGroup.layout(ViewGroup.java:4631)
E/AndroidRuntime( 1418):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
E/AndroidRuntime( 1418):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
E/AndroidRuntime( 1418):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
E/AndroidRuntime( 1418):    at android.view.View.layout(View.java:14838)
E/AndroidRuntime( 1418):    at android.view.ViewGroup.layout(ViewGroup.java:4631)
E/AndroidRuntime( 1418):    at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1626)
E/AndroidRuntime( 1418):    at android.view.View.layout(View.java:14838)
E/AndroidRuntime( 1418):    at android.view.ViewGroup.layout(ViewGroup.java:4631)
E/AndroidRuntime( 1418):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
E/AndroidRuntime( 1418):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
E/AndroidRuntime( 1418):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
E/AndroidRuntime( 1418):    at android.view.View.layout(View.java:14838)
E/AndroidRuntime( 1418):    at android.view.ViewGroup.layout(ViewGroup.java:4631)
E/AndroidRuntime( 1418):    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
E/AndroidRuntime( 1418):    at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
E/AndroidRuntime( 1418):    at android.view.View.layout(View.java:14838)
E/AndroidRuntime( 1418):    at android.view.ViewGroup.layout(ViewGroup.java:4631)
E/AndroidRuntime( 1418):    at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1055)
E/AndroidRuntime( 1418):    at android.view.View.layout(View.java:14838)
E/AndroidRuntime( 1418):    at android.view.ViewGroup.layout(ViewGroup.java:4631)
E/AndroidRuntime( 1418):    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
E/AndroidRuntime( 1418):    at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
E/AndroidRuntime( 1418):    at android.view.View.layout(View.java:14838)
E/AndroidRuntime( 1418):    at android.view.ViewGroup.layout(ViewGroup.java:4631)
E/AndroidRuntime( 1418):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
E/AndroidRuntime( 1418):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
E/AndroidRuntime( 1418):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
E/AndroidRuntime( 1418):    at android.view.View.layout(View.java:14838)
E/AndroidRuntime( 1418):    at android.view.ViewGroup.layout(ViewGroup.java:4631)
E/AndroidRuntime( 1418):    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
E/AndroidRuntime( 1418):    at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
E/AndroidRuntime( 1418):    at android.view.View.layout(View.java:14838)
E/AndroidRuntime( 1418):    at android.view.ViewGroup.layout(ViewGroup.java:4631)
E/AndroidRuntime( 1418):    at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1996)
E/AndroidRuntime( 1418):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1753)
E/AndroidRuntime( 1418):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1005)
E/AndroidRuntime( 1418):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5750)
E/AndroidRuntime( 1418):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
E/AndroidRuntime( 1418):    at android.view.Choreographer.doCallbacks(Choreographer.java:574)
E/AndroidRuntime( 1418):    at android.view.Choreographer.doFrame(Choreographer.java:544)
E/AndroidRuntime( 1418):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
E/AndroidRuntime( 1418):    at android.os.Handler.handleCallback(Handler.java:733)
E/AndroidRuntime( 1418):    at android.os.Handler.dispatchMessage(Handler.java:95)
E/AndroidRuntime( 1418):    at android.os.Looper.loop(Looper.java:136)
E/AndroidRuntime( 1418):    at android.app.ActivityThread.main(ActivityThread.java:5017)
E/AndroidRuntime( 1418):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime( 1418):    at java.lang.reflect.Method.invoke(Method.java:515)
E/AndroidRuntime( 1418):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
E/AndroidRuntime( 1418):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:610)
E/AndroidRuntime( 1418):    at dalvik.system.NativeStart.main(Native Method)

activiy xml是：

        <android.support.v4.view.ViewPager
            android:id="@+id/pager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
        android:layout_marginBottom="1dp"
        android:layout_weight="1" />

        <com.viewpagerindicator.CirclePageIndicator
            android:id="@+id/pagerIndicator"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:padding="3dp"
            android:layout_gravity="bottom|center_horizontal"
            android:layout_marginBottom="5dp"
            android:layout_weight="5" />

grid.xml是：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >

<GridView
    android:id="@+id/gridView"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_margin="10dp"
    android:layout_marginTop="10dp"
    android:horizontalSpacing="100dp"
    android:listSelector="@android:color/transparent"
    android:numColumns="4"
    android:stretchMode="columnWidth"
    android:verticalSpacing="2dp" />

grid_item xml是：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/app_grid_item"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:padding="@dimen/app_margin">

<ImageView
    android:id="@+id/app_icon"
    android:layout_width="@dimen/grid_icon_width"
    android:layout_height="@dimen/grid_icon_height"
    android:layout_centerHorizontal="true"
    android:visibility="visible" />

<RelativeLayout
    android:id="@+id/label_container"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@+id/app_icon"
    android:layout_alignParentBottom="true">

    <TextView
        android:id="@+id/app_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center_horizontal"
        android:minWidth="20dp"
        android:ellipsize="end"
        android:singleLine="true"
        android:padding="4dp"
        android:textSize="15sp" />
</RelativeLayout>

GridAdapter是：

public class GridAdapter extends BaseAdapter {

Context context;

private GridItems[] items;
private LayoutInflater mInflater;

public class ViewHolder {
    public ImageView imageView;
    public TextView textTitle;
}

public GridAdapter(Context context, GridItems[] items) {

    mInflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.context = context;
    this.items = items;

}

...

@Override
public void notifyDataSetChanged() {
    super.notifyDataSetChanged();
}

@Override
public Object getItem(int position) {
    if (items != null && position >= 0 && position < getCount()) {
        return items[position];
    }
    return null;
}

@Override
public long getItemId(int position) {
    if (items != null && position >= 0 && position < getCount()) {
        return items[position].id;
    }
    return 0;
}

public void setItemsList(GridItems[] locations) {
    this.items = locations;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder viewHolder;

    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.app_grid_item, parent, false);
        viewHolder = new ViewHolder();
        viewHolder.imageView = ((ImageView) convertView.findViewById(R.id.app_icon));
        viewHolder.textTitle =  ((TextView) convertView.findViewById(R.id.app_name));
        convertView.setTag(viewHolder);
    } else {
        viewHolder = (ViewHolder) convertView.getTag();
    }
    GridItems gridItems = items[position];
    viewHolder.imageView.setImageDrawable(gridItems.appInfo.icon);
    viewHolder.textTitle.setText(gridItems.appInfo.name);
    Log.v(TAG, "The position is " + position + ", " + gridItems.appInfo.packageName + " getView");

    return convertView;
}

}

FragmentStatePagerAdapter是：

   private class MyPagerAdapter extends FragmentStatePagerAdapter {
    private List<GridFragment> fragments;
    FragmentManager fm;

    public MyPagerAdapter(FragmentManager fm, List<GridFragment> gridFragments) {
        super(fm);
        this.fm = fm;
        this.fragments = gridFragments;
    }

    @Override
    public GridFragment getItem(int position) {
        return this.fragments.get(position);
    }

    @Override
    public int getCount() {
        return this.fragments.size();
    }
}

}

Answer 1

空指针似乎在您的getView()方法中。使用以下内容确定哪个项为空：

public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder viewHolder;

    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.app_grid_item, parent, false);
        viewHolder = new ViewHolder();
        viewHolder.imageView = ((ImageView) convertView.findViewById(R.id.app_icon));
        viewHolder.textTitle =  ((TextView) convertView.findViewById(R.id.app_name));
        convertView.setTag(viewHolder);
    } else {
        viewHolder = (ViewHolder) convertView.getTag();
    }
    if (viewHolder == null) {
        Log.e("GridAdapter", "viewHolder was null")
        return convertView;
    }
    GridItems gridItems = items[position];
    if (gridItems == null || gridItems.appInfo == null) {
        Log.e("GridAdapter", "gridItems or appInfo was null")
        return convertView;
    }
    viewHolder.imageView.setImageDrawable(gridItems.appInfo.icon);
    viewHolder.textTitle.setText(gridItems.appInfo.name);
    Log.v(TAG, "The position is " + position + ", " + gridItems.appInfo.packageName + " getView");

    return convertView;
}

当使用gridview滑动片段时，会发生java.lang.NullPointerException

1 个答案: