Question

我对此代码有疑问。我试图从firebase数据库传递检索到的字符串图像，但它一直崩溃，Firebasye显示此错误：异常java.lang.NullPointerException：尝试调用虚方法＆＃39; java.lang.String com。 example.vujeva.Task.getImage（）＆＃39;在null对象引用上 com.example.vujeva.MainActivity $ BlogViewHolder.onClick（MainActivity.java:161）

这是我的MainActivity：

    public class MainActivity extends AppCompatActivity {

public static final String TASK_NAME = "com.example.vujeva.tutorshare.title";
public static final String TASK_DESC = "com.example.vujeva.tutorshare.desc";
public static final String TASK_IMAGE = "com.example.vujeva.tutorshare.image";
private RecyclerView mBlogList;

//private ListView mTaskList;
private DatabaseReference mDatabase;
List<Task> artists;
private FloatingActionButton fab;
//private ListView lv;
ArrayAdapter<String> adapter;
String key;
CardView card_view;
ImageView viewy;View inflatedView;
    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //mTaskList = (ListView) findViewById(R.id.task_list);
    mDatabase = FirebaseDatabase.getInstance().getReference().child("Task");
    mBlogList = (RecyclerView)findViewById(R.id.task_list);
    mBlogList.setHasFixedSize(true);
    mBlogList.setLayoutManager(new LinearLayoutManager(this));

    //mTaskList.setHasFixedSize(true);
    //mTaskList.setLayoutManager(new LinearLayoutManager(this));
    artists = new ArrayList<>();
    fab = (FloatingActionButton) findViewById(R.id.fab);

    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(MainActivity.this, AddActivity.class);
            startActivity(intent);
        }
    });        
}

@Override
protected void onStart() {
    super.onStart();
    FirebaseRecyclerAdapter<Task, BlogViewHolder> firebaseRecyclerAdapter =
            new FirebaseRecyclerAdapter<Task, BlogViewHolder>(
                    Task.class,
                    R.layout.design_row,
                    BlogViewHolder.class,
                    mDatabase){
                protected void populateViewHolder(final BlogViewHolder viewHolder,final Task model, int position) {
                    ImageView post_image = (ImageView) findViewById(R.id.imageViewy);
                    viewHolder.setTitle(model.getTitle());
                    viewHolder.setImage(getApplicationContext(), model.getImage());
                    }
                };

    mBlogList.setAdapter(firebaseRecyclerAdapter);

}

public static class BlogViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
    View mView;
    private ArrayList<Task> mPhotos;
    Task model;
    ImageView postCommentLayout;
    public BlogViewHolder(View itemView) {
        super(itemView);
        mView= itemView;
        postCommentLayout = (ImageView) itemView.findViewById(R.id.imageViewy);
        itemView.setOnClickListener(this);
    }
    public void setTitle(String title){
        TextView post_title = (TextView)mView.findViewById(R.id.titleText);
        post_title.setText(title);
    }
    public void setImage(Context ctx , String image){
        ImageView post_image = (ImageView)mView.findViewById(R.id.imageViewy);
        // We Need TO pass Context
        Picasso.with(ctx).load(image).into(post_image);
        }

    @Override
    public void onClick(View itemView) {

        Context context = itemView.getContext();
        Intent showPhotoIntent = new Intent(context, ActionActivity.class);
        showPhotoIntent.putExtra(TASK_IMAGE, model.getImage().toString());
        context.startActivity(showPhotoIntent);
    }
}

这是我的ActionActivity：

    public class ActionActivity extends MainActivity {
private CollapsingToolbarLayout collapsingToolbarLayout = null;
private RecyclerView mImageTask;
private DatabaseReference mDatabase;
private ImageView mImage;
Intent intent;
public Uri mImageUri = null;
List<Task> artists;
String image;
private Task mPost;
public static final String TASK_IMAGE = "com.example.vujeva.tutorshare.image";
public static final String DATABASE_PATH_UPLOADS = "Tasks";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_action);
    Intent intent = getIntent();

    image = intent.getStringExtra(MainActivity.TASK_IMAGE);
    mImage = (ImageView) findViewById(R.id.profile_id);

    Picasso.with(this).load(image).into(mImage);


}


private void toolbarTextAppernce() {
    collapsingToolbarLayout.setCollapsedTitleTextAppearance(R.style.collapsedappbar);
    collapsingToolbarLayout.setExpandedTitleTextAppearance(R.style.expandedappbar);
}

Answer 1

在CommandLineRunner中，您声明了BlogViewHolder但从未初始化。在Task model;，您拨打onClick()，但model.getImage().toString()仍为空。

Answer 2

在protected void populateViewHolder

中

  protected void populateViewHolder(final BlogViewHolder viewHolder,final Task model, int position) {
                ImageView post_image = (ImageView) findViewById(R.id.imageViewy);
                viewHolder.setTitle(model.getTitle());
              //  viewHolder.setImage(getApplicationContext(), model.getImage());

Picasso.with(viewHolder.imageView.getContext()).load(model.getUrl()).into(viewHolder.imageView);  //use this
                }
            };

Firebase数据库图像字符串传递到另一个活动

2 个答案: