Android 使用CustomAdapter更新GridView中的ImageView

我有个问题

我遇到的问题是：

java.lang.NullPointerException: Attempt to invoke interface method 
'java.lang.Object java.util.Map.get(java.lang.Object)' on a null object reference

我试图做的是将ArrayList（包含Hashmap）传递给自定义GridViewAdapter，这样我就可以根据文件名将ImageView设置为特定的电子邮件。以下是我的两个类的代码：

ClaimFilesActivity.java

谢谢

编辑：LOGCAT:

07-27 16:18:29.661  11561-11561/com.tutecentral.navigationdrawer E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.tutecentral.navigationdrawer, PID: 11561
java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object java.util.Map.get(java.lang.Object)' on a null object reference
        at com.tutecentral.navigationdrawer.GridViewFilesAdapter.getView(GridViewFilesAdapter.java:44)
        at android.widget.AbsListView.obtainView(AbsListView.java:2347)
        at android.widget.GridView.onMeasure(GridView.java:1060)
        at android.view.View.measure(View.java:17547)
        at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727)
        at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463)
        at android.view.View.measure(View.java:17547)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
        at android.view.View.measure(View.java:17547)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
        at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:447)
        at android.view.View.measure(View.java:17547)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2615)
        at android.view.View.measure(View.java:17547)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2015)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1173)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1379)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5885)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
        at android.view.Choreographer.doCallbacks(Choreographer.java:580)
        at android.view.Choreographer.doFrame(Choreographer.java:550)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5254)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

换衣服

---

@覆盖公共对象getItem（int位置）{return null}

到

---

@重写公共对象getItem（int位置）{return dataList.get（position）；}

---

你不能将null/整数作为对象返回。

你能添加整个logcat报告并告诉我们null对象在哪一行吗？不管怎样，我看到你在末尾添加了它。我还是添加了logcat

@Override public object getItem（int position）{return null；}

我认为你不能将null转换为字符串（）.您应该在该位置获取项目，而不是该位置本身。。。尝试

返回dataList.get（位置）
public class GridViewFilesAdapter extends BaseAdapter {
private Context context;
ArrayList<LinkedHashMap<String, String>> dataList;

public GridViewFilesAdapter(Context context, ArrayList<LinkedHashMap<String, String>> oslist) {
    this.context = context;
    this.dataList = oslist;
}

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

    LayoutInflater inflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    View gridView;

    if (convertView == null) {

        gridView = new View(context);

        // get layout from mobile.xml
        gridView = inflater.inflate(R.layout.grid_row, null);

        // set value into textview
        TextView textView = (TextView) gridView
                .findViewById(R.id.fileName);
        textView.setText(((Map)getItem(position)).get("file_name").toString());
        // set image based on selected text
        ImageView imageView = (ImageView) gridView
                .findViewById(R.id.fileImg);


        if (((Map)getItem(position)).get("file_filename").toString().endsWith(".pdf")) {
            imageView.setImageResource(R.mipmap.ic_pdf_filetype);
        } else {
            imageView.setImageResource(R.mipmap.ic_docx_filetype);
        }

    } else {
        gridView = (View) convertView;
    }

    return gridView;
}

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

@Override
public Object getItem(int position) {
    return null;
}

@Override
public long getItemId(int position) {
    return 0;
}

}

textView.setText(((Map)getItem(position)).get("file_name").toString());

07-27 16:18:29.661  11561-11561/com.tutecentral.navigationdrawer E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.tutecentral.navigationdrawer, PID: 11561
java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object java.util.Map.get(java.lang.Object)' on a null object reference
        at com.tutecentral.navigationdrawer.GridViewFilesAdapter.getView(GridViewFilesAdapter.java:44)
        at android.widget.AbsListView.obtainView(AbsListView.java:2347)
        at android.widget.GridView.onMeasure(GridView.java:1060)
        at android.view.View.measure(View.java:17547)
        at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727)
        at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463)
        at android.view.View.measure(View.java:17547)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
        at android.view.View.measure(View.java:17547)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
        at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:447)
        at android.view.View.measure(View.java:17547)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2615)
        at android.view.View.measure(View.java:17547)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2015)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1173)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1379)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5885)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
        at android.view.Choreographer.doCallbacks(Choreographer.java:580)
        at android.view.Choreographer.doFrame(Choreographer.java:550)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5254)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)