如何在 RecyclerView 中实现 StartActivityForResult

Posted 2023-02-19

【中文标题】如何在 RecyclerView 中实现 StartActivityForResult

【英文标题】：How to implement StartActivityForResult in RecyclerView

【发布时间】：2018-07-19 16:07:21

【问题描述】：

我正在尝试在我的 RecyclerView 中使用 startActivityForResult 并且不知道如何...尝试了这种方式，我从 Activity 获得了 NullPointExeption，有什么办法可以解决它。

这是活动：

    RecyclerView recyclerView=findViewById(R.id.todo_Recyclerview);
    Todo_Adapter adapter=new Todo_Adapter(this,Todo_DataGenerator.getData(this));
    recyclerView.setLayoutManager(new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false));
    recyclerView.setAdapter(adapter);


TextView title=findViewById(R.id.todo_txt_Titleitem);
TextView content=findViewById(R.id.todo_txt_Contentitem);


@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) 
    super.onActivityResult(requestCode, resultCode, data);


    if (requestCode== Request &&
            resultCode==RESULT_OK &&
            data !=null)

        String Title=data.getStringExtra(Todo_saveActivity.Todo_Title);
        String Content=data.getStringExtra(Todo_saveActivity.Todo_Content);

        title.setText(Title);
        content.setText(Content);

这是适配器：

public class Todo_Adapter extends RecyclerView.Adapter<Todo_Adapter.Todo_itemViewHolder> 
public static final int Request = 1002;

private Context context;
private List<Todo_SampleClass> Notes;



public Todo_Adapter(Context context, List<Todo_SampleClass> Notes) 

    this.context = context;
    this.Notes = Notes;



@Override
public Todo_itemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) 
    LayoutInflater layoutInflater = LayoutInflater.from(context);
    View view = layoutInflater.inflate(R.layout.todo_rv_item, parent, false);
    return new Todo_itemViewHolder(view);




@Override
public void onBindViewHolder(Todo_itemViewHolder holder, int position) 
    holder.bindNotes(Notes.get(position));
    holder.Add.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View v) 
            Intent intent=new Intent(context, Todo_saveActivity.class);
            ((Activity) context).startActivityForResult(intent,Request);

        
    );




@Override
public int getItemCount() 
    return Notes.size();


public class Todo_itemViewHolder extends RecyclerView.ViewHolder 

    private TextView Title;
    private TextView Content;
    private ImageButton edit;
    private ImageButton remove;
    private Button Add;

    public Todo_itemViewHolder(View itemView) 
        super(itemView);
        Title = itemView.findViewById(R.id.todo_txt_Titleitem);
        Content = itemView.findViewById(R.id.todo_txt_Contentitem);
        edit = itemView.findViewById(R.id.todo_btn_edit);
        remove = itemView.findViewById(R.id.todo_btn_remove);
        Add = itemView.findViewById(R.id.todo_btn_add);

    


    public void bindNotes(Todo_SampleClass Notes) 
        Title.setText(Notes.getTitle());
        Content.setText(Notes.getContent());
        edit.setImageDrawable(Notes.getImgbtn_edit());

        remove.setImageDrawable(Notes.getImgbtn_remove());
    

    

这是我要参加的第二个活动：

public class Todo_saveActivity extends AppCompatActivity 


public static final String Todo_Title ="result";
public static final String Todo_Content="content";
@Override
protected void onCreate(Bundle savedInstanceState) 
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_todo_save);


    final EditText Title=findViewById(R.id.todo_name);
   final EditText Content=findViewById(R.id.todo_family);

这是 logcat：

  java.lang.RuntimeException: Unable to instantiate activity ComponentInfocom.example.expert2.expert2/com.example.expert2.expert2.rv_Todo.Todo_rv: java.lang.NullPointerException
                  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2137)
                  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
                  at android.app.ActivityThread.access$600(ActivityThread.java:141)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
                  at android.os.Handler.dispatchMessage(Handler.java:99)
                  at android.os.Looper.loop(Looper.java:137)
                  at android.app.ActivityThread.main(ActivityThread.java:5103)
                  at java.lang.reflect.Method.invokeNative(Native Method)
                  at java.lang.reflect.Method.invoke(Method.java:525)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
                  at dalvik.system.NativeStart.main(Native Method)
               Caused by: java.lang.NullPointerException
                  at android.support.v7.app.AppCompatDelegateImplBase.<init>(AppCompatDelegateImplBase.java:117)
                  at android.support.v7.app.AppCompatDelegateImplV9.<init>(AppCompatDelegateImplV9.java:149)
                  at android.support.v7.app.AppCompatDelegateImplV11.<init>(AppCompatDelegateImplV11.java:29)
                  at android.support.v7.app.AppCompatDelegateImplV14.<init>(AppCompatDelegateImplV14.java:54)
                  at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:202)
                  at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:183)
                  at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:519)
                  at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:190)
                  at com.example.expert2.expert2.rv_Todo.Todo_rv.<init>(Todo_rv.java:29)
                  at java.lang.Class.newInstanceImpl(Native Method)
                  at java.lang.Class.newInstance(Class.java:1130)
                  at android.app.Instrumentation.newActivity(Instrumentation.java:1061)

谢谢。---------------------------------------------- ---------------------

【问题讨论】：

在你的适配器中，你从哪里得到变量context？

【参考方案1】：

查看这段代码时：

public static final int Request = 1002;

 @Override
public void onBindViewHolder(Todo_itemViewHolder holder, int position) 
    holder.bindNotes(Notes.get(position));
    holder.Add.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View v) 
            Intent intent=new Intent(context, Todo_saveActivity.class);
            ((Activity) context).startActivityForResult(intent,Request);

        
    );

在我看来，（（活动）上下文）似乎是问题所在。您正在尝试使用为空的 Activity 对象调用 startActivityForResult(...) 。根据您的 RecyclerView 是在 Activity 中还是在 Fragment 中，请确保您将 context 设置为等于父 Activity 上下文的有效实例，例如：

Context context = getContext(); //if in fragment
Context context = (Context)this; //if in parent activity

然后你应该可以打电话了

((Activity) context).startActivityForResult(intent,Request);

没有任何问题。

【讨论】：

谢谢...家长活动你的意思是第一个活动？我的 RecyclerView 是活动，但不是第一个......我应该在哪里添加？

如果您使用的是片段，则父活动是片段所在的活动。

【参考方案2】：

如果您愿意使用回调来执行此操作，而不是直接在您的活动中执行此操作...

创建一个这样的界面：

public interface OnBindCallback 
    void onViewBound(Todo_itemViewHolder viewHolder, int position);

然后，在您的适配器中：

public OnBindCallback onBind;

@Override public void onBindViewHolder(Todo_itemViewHolder holder, int position) 
    if (onBind != null) 
        onBind.onViewBound(holder, position);
    

最后，在你的活动中：

adapter.onBind = (viewHolder, position) -> 
    viewHolder.itemView.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View view) 
            Intent intent=new Intent(YourActivityName.this, Todo_saveActivity.class);
            YourActivityName.this.startActivityForResult(intent, 1002);
        
    );
;