Question

我创建了一个imageviewer应用。它的工作正常但是当我选择一个gridview项来删除它时，它就会停止工作。选择项目时，会出现删除按钮。单击删除按钮时，会出现一个警告对话框，要求确认。我希望在按下YES按钮后删除该文件。但它不会发生。相反，它会抛出indexoutofbounds异常。如何成功删除所选文件？

PhotosActivity.java

import static com.example.dell_1.myapp3.ImageViewer.ImageGallery.al_images;

public class PhotosActivity extends AppCompatActivity {
    int int_position;
    private GridView gridView;
    GridViewAdapter adapter;
    ArrayList<Model_images> al_menu = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_image_gallery);

        final ImageButton button1 = (ImageButton) findViewById(R.id.button1);
        final ImageButton button2 = (ImageButton) findViewById(R.id.button2);
        final ImageButton button3 = (ImageButton) findViewById(R.id.button3);
        final ImageButton button4 = (ImageButton) findViewById(R.id.button4);
        final ImageButton button5 = (ImageButton) findViewById(R.id.button5);
        button1.setVisibility(View.GONE);
        button2.setVisibility(View.GONE);
        button3.setVisibility(View.GONE);
        button4.setVisibility(View.GONE);
        button5.setVisibility(View.GONE);

        gridView = (GridView) findViewById(android.R.id.list);
        int_position = getIntent().getIntExtra("value", 0);
        adapter = new GridViewAdapter(this, al_images, int_position);
        gridView.setAdapter(adapter);

        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                String abc = "file://" + al_images.get(int_position).getAl_imagepath().get(position);

                Intent i = new Intent(getApplicationContext(), FullImageActivity.class);
                i.putExtra("id", position);
                i.putExtra("folderPosition", int_position);
                i.putExtra("abc", abc);
                startActivity(i);
            }
        });

        gridView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
                for (int j = 0; j < parent.getChildCount(); j++)
                    parent.getChildAt(j).setBackgroundColor(Color.TRANSPARENT);

                // change the background color of the selected element
                view.setBackgroundColor(Color.LTGRAY);
                button1.setVisibility(View.VISIBLE);
                button2.setVisibility(View.VISIBLE);
                button3.setVisibility(View.VISIBLE);
                button4.setVisibility(View.VISIBLE);
                button5.setVisibility(View.VISIBLE);
                button3.setOnClickListener(
                        new View.OnClickListener() {
                            public void onClick(View view) {
                                AlertDialog.Builder builder1 = new AlertDialog.Builder(PhotosActivity.this);
                                builder1.setMessage("Are you sure you want to delete it ?");
                                builder1.setCancelable(true);

                                builder1.setPositiveButton(
                                        "Yes",
                                        new DialogInterface.OnClickListener() {
                                            public void onClick(DialogInterface dialog, int id) {
                                                File file = new File( al_menu.get(int_position).getAl_imagepath().get(position));
                                                file.delete();
                                               al_menu.remove(position);
                                                adapter.notifyDataSetChanged();
                                            }
                                        });

                                builder1.setNegativeButton(
                                        "No",
                                        new DialogInterface.OnClickListener() {
                                            public void onClick(DialogInterface dialog, int id) {
                                                dialog.cancel();
                                            }
                                        });

                                AlertDialog alert11 = builder1.create();
                                alert11.show();
                            }
                        });
                return true;
            }
        });


    }
}

ImageGallery.java ：

public class ImageGallery extends AppCompatActivity {
    public static ArrayList<Model_images> al_images = new ArrayList<>();
    boolean boolean_folder;
    Adapter_PhotosFolder obj_adapter;
    GridView gv_folder;
    private static final int REQUEST_PERMISSIONS = 100;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_image_gallery);
        gv_folder = (GridView) findViewById(android.R.id.list);

        final ImageButton button1 = (ImageButton) findViewById(R.id.button1);
        final ImageButton button2 = (ImageButton) findViewById(R.id.button2);
        final ImageButton button3 = (ImageButton) findViewById(R.id.button3);
        final ImageButton button4 = (ImageButton) findViewById(R.id.button4);
        final ImageButton button5 = (ImageButton) findViewById(R.id.button5);
        button1.setVisibility(View.GONE);
        button2.setVisibility(View.GONE);
        button3.setVisibility(View.GONE);
        button4.setVisibility(View.GONE);
        button5.setVisibility(View.GONE);

        gv_folder.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                Intent intent = new Intent(getApplicationContext(), PhotosActivity.class);
                intent.putExtra("value",i);
                startActivity(intent);
            }
        });

GridViewAdapter.java ：

public class GridViewAdapter extends ArrayAdapter<Model_images> {

    Context context;
    ViewHolder viewHolder;
    ArrayList<Model_images> al_menu = new ArrayList<>();
    int int_position;


    public GridViewAdapter(Context context, ArrayList<Model_images> al_menu,int int_position) {
        super(context, R.layout.activity_adapter__photos_folder, al_menu);
        this.al_menu = al_menu;
        this.context = context;
        this.int_position = int_position;
    }

    @Override
    public int getCount() {

        Log.e("ADAPTER LIST SIZE", al_menu.get(int_position).getAl_imagepath().size() + "");
        return al_menu.get(int_position).getAl_imagepath().size();
    }

    @Override
    public int getItemViewType(int position) {
        return position;
    }

    @Override
    public int getViewTypeCount() {
        if (al_menu.get(int_position).getAl_imagepath().size() > 0) {
            return al_menu.get(int_position).getAl_imagepath().size();
        } else {
            return 1;
        }
    }

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


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

        if (convertView == null) {

            viewHolder = new ViewHolder();
            convertView = LayoutInflater.from(getContext()).inflate(R.layout.activity_adapter__photos_folder, parent, false);
            viewHolder.tv_foldern = (TextView) convertView.findViewById(R.id.tv_folder);
            viewHolder.tv_foldersize = (TextView) convertView.findViewById(R.id.tv_folder2);
            viewHolder.iv_image = (ImageView) convertView.findViewById(R.id.iv_image);


            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        viewHolder.tv_foldern.setVisibility(View.GONE);
        viewHolder.tv_foldersize.setVisibility(View.GONE);



        Glide.with(context).load("file://" + al_menu.get(int_position).getAl_imagepath().get(position))
                .diskCacheStrategy(DiskCacheStrategy.NONE)
                .skipMemoryCache(true)
                .into(viewHolder.iv_image);


        return convertView;

    }

    private static class ViewHolder {
        TextView tv_foldern, tv_foldersize;
        ImageView iv_image;

    }
}

logcat的：

10-20 17:27:02.769 24402-24402/com.example.dell_1.Myapp3 E/AndroidRuntime: FATAL EXCEPTION: main
                                                                           Process: com.example.dell_1.Myapp3, PID: 24402
                                                                           java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
                                                                               at java.util.ArrayList.get(ArrayList.java:411)
                                                                               at com.example.dell_1.myapp3.ImageViewer.PhotosActivity$2$1$1.onClick(PhotosActivity.java:85)
                                                                               at android.support.v7.app.AlertController$ButtonHandler.handleMessage(AlertController.java:161)
                                                                               at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                               at android.os.Looper.loop(Looper.java:154)
                                                                               at android.app.ActivityThread.main(ActivityThread.java:6077)
                                                                               at java.lang.reflect.Method.invoke(Native Method)
                                                                               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
                                                                               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

Answer 1

根据您的代码，我看不到ArrayList al_menu在哪里加载数据。因此，当您的onClick执行并尝试在索引0处获取项时，您将获得IndexOutOfBoundsException异常。看起来你必须提供默认值。同样在GridViewAdapter内部，您可以在文件顶部声明并实例化al_menu，然后在构造函数内覆盖它。这是不必要的，导致额外的对象被使用和丢弃，并且不会在适配器中保护NullPointerException，因为null可以传递给GridViewAdapter的构造函数，并且您不检查以确保这一点。我建议添加一个条件，检查传入的ArrayList是否为null，并使用for循环将值添加到ArrayList，甚至从文件顶部删除实例化行，并在GridViewAdapter的构造函数中执行，并在ArrayList中使用作为参数的参数，如果在实例化al_menu时它不是null作为参数。例如：

public class GridViewAdapter extends ArrayAdapter<Model_images> {

Context context;
ViewHolder viewHolder;
ArrayList<Model_images> al_menu;
int int_position;


public GridViewAdapter(Context context, ArrayList<Model_images> al_menu,int int_position) {
    super(context, R.layout.activity_adapter__photos_folder, al_menu);
    if(al_menu != null) {
       this.al_menu = new ArrayList(al_menu);
    }
    this.context = context;
    this.int_position = int_position;
}

@Override
public int getCount() {

    Log.e("ADAPTER LIST SIZE", al_menu.get(int_position).getAl_imagepath().size() + "");
    return al_menu.get(int_position).getAl_imagepath().size();
}

@Override
public int getItemViewType(int position) {
    return position;
}

@Override
public int getViewTypeCount() {
    if (al_menu.get(int_position).getAl_imagepath().size() > 0) {
        return al_menu.get(int_position).getAl_imagepath().size();
    } else {
        return 1;
    }
}

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


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

    if (convertView == null) {

        viewHolder = new ViewHolder();
        convertView = LayoutInflater.from(getContext()).inflate(R.layout.activity_adapter__photos_folder, parent, false);
        viewHolder.tv_foldern = (TextView) convertView.findViewById(R.id.tv_folder);
        viewHolder.tv_foldersize = (TextView) convertView.findViewById(R.id.tv_folder2);
        viewHolder.iv_image = (ImageView) convertView.findViewById(R.id.iv_image);


        convertView.setTag(viewHolder);
    } else {
        viewHolder = (ViewHolder) convertView.getTag();
    }

    viewHolder.tv_foldern.setVisibility(View.GONE);
    viewHolder.tv_foldersize.setVisibility(View.GONE);



    Glide.with(context).load("file://" + al_menu.get(int_position).getAl_imagepath().get(position))
            .diskCacheStrategy(DiskCacheStrategy.NONE)
            .skipMemoryCache(true)
            .into(viewHolder.iv_image);


    return convertView;

}

private static class ViewHolder {
    TextView tv_foldern, tv_foldersize;
    ImageView iv_image;

}
}

从网格视图SD卡中删除所选图像

1 个答案: