添加的项目未显示在我的 RecyclerView 中答案

【问题标题】：Added items are not showing in my RecyclerView添加的项目未显示在我的 RecyclerView 中
【发布时间】：2019-07-21 08:00:54
【问题描述】：

所以我创建了一个简单的应用程序，让用户添加一个项目（图像、姓名和年龄），当单击提交按钮时，这些项目将通过 recyclerView 显示在 MainActivity 中。

我下面代码的问题是，当我点击保存按钮时，我的应用程序将关闭。

看看我下面的代码：

MainActivity.java

public class MainActivity extends AppCompatActivity {

    Uri imageUri;
    ArrayList<Person> personArrayList = new ArrayList<>();
    private RecyclerView mRecyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;
    private CoordinatorLayout coordinatorLayout;

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

        //
        mRecyclerView = findViewById(R.id.recyclerview);
        mRecyclerView.setHasFixedSize(true);
        mLayoutManager = new LinearLayoutManager(this);
        mAdapter = new PersonAdapter(personArrayList);

        mRecyclerView.setLayoutManager(mLayoutManager);
        mRecyclerView.setAdapter(mAdapter);
        //

        mRecyclerView = (RecyclerView) findViewById(R.id.recyclerview);
        mAdapter = new PersonAdapter(personArrayList);
        mAdapter.notifyDataSetChanged();
        mRecyclerView.setAdapter(mAdapter);

    }

    //for menu

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.add_menu, menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        switch (id){
            case R.id.action_add:
                Intent add = new Intent(MainActivity.this, AddPersonActivity.class);
                startActivityForResult(add, 0);
                break;
        }

        return super.onOptionsItemSelected(item);
    }

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

        if (resultCode == Activity.RESULT_OK) {
            Bundle bundle = data.getExtras();
            imageUri = bundle.getParcelable("image");
            String name = bundle.getString("name");
            String age = bundle.getString("age");

            Person person = new Person(imageUri, name, age);
            //
            switch (requestCode){
                case 0: //request to add new person
                    personArrayList.add(person);
                    Snackbar snackbar = Snackbar
                            .make(coordinatorLayout, "New person added.", Snackbar.LENGTH_INDEFINITE)
                            .setAction("UNDO", new View.OnClickListener() {
                                @Override
                                public void onClick(View v) {
                                    Snackbar snackbar1 = Snackbar
                                            .make(coordinatorLayout, "Undo successful.", Snackbar.LENGTH_SHORT);
                                    snackbar1.show();
                                }
                            })
                            .setActionTextColor(Color.RED);
                    snackbar.show();
                    break;
            }

        }else{

        }
    }
}

AddPersonActivity.java

public class AddPersonActivity extends AppCompatActivity implements View.OnClickListener {

    Uri imageUri;
    ImageView personiv;
    EditText person_name, person_age;
    Button btnsave, btncancel;
    PersonAdapter adapter;
    private static final int PICK_IMAGE = 100;

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

        //instantiate
        personiv = (ImageView) findViewById(R.id.imageview2);
        person_name = (EditText) findViewById(R.id.edittextname);
        person_age = (EditText) findViewById(R.id.edittextage);

        btnsave = (Button) findViewById(R.id.btnsave);
        btncancel = (Button) findViewById(R.id.btncancel);


        personiv.setOnClickListener(this);
        btnsave.setOnClickListener(this);
        btncancel.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        int sid = v.getId();

        switch (sid){
            case R.id.imageview2:
                Intent gallery = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.INTERNAL_CONTENT_URI);
                startActivityForResult(gallery, PICK_IMAGE);
                break;
            case R.id.btnsave:
                String name = person_name.getText().toString();
                String age = person_age.getText().toString();

                if(!name.equals("") && !age.equals("")){
                    Intent intent = new Intent(); //blind intent
                    intent.putExtra("image", this.imageUri);
                    intent.putExtra("name", name);
                    intent.putExtra("age", age);

                    this.setResult(Activity.RESULT_OK, intent);
                    finish();
                }else{
                    Toast.makeText(getApplicationContext(), "Fill in all fields!", Toast.LENGTH_SHORT).show();
                }
                break;
            case R.id.btncancel:
                personiv.setImageResource(R.drawable.add_user);
                person_name.setText("");
                person_age.setText("");
                break;
        }
    }

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

        if(requestCode != 0){
            if(data != null){
                imageUri = data.getData();
                personiv.setImageURI(imageUri);
            }//end if
        }else{
            /////
        }
    }
}

PersonAdapter.java

public class PersonAdapter extends RecyclerView.Adapter<PersonAdapter.PersonViewHolder> {

    private ArrayList<Person> mpersonArrayList;

    public static class PersonViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{

        public ImageView mImage;
        public TextView mName, mAge;
        LinearLayout customlayout;

        public PersonViewHolder(@NonNull View itemView) {
            super(itemView);
            mImage = (ImageView) itemView.findViewById(R.id.imageview1);
            mName = (TextView) itemView.findViewById(R.id.textname);
            mAge = (TextView) itemView.findViewById(R.id.textage);

        }

        @Override
        public void onClick(View v) {

        }
    }

    public PersonAdapter(ArrayList<Person> personArrayList){
        mpersonArrayList = personArrayList;
    }

    @NonNull
    @Override
    public PersonViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.custom_layout, viewGroup, false);
        PersonViewHolder pvholder = new PersonViewHolder(view);
        return pvholder;
    }

    @Override
    public void onBindViewHolder(@NonNull PersonViewHolder personViewHolder, int i) {
        Person currentItem = mpersonArrayList.get(i);

        personViewHolder.mImage.setImageURI(currentItem.getmImage());
        personViewHolder.mName.setText(currentItem.getmName());
        personViewHolder.mAge.setText(currentItem.getmAge());

    }

    @Override
    public int getItemCount() {
        return mpersonArrayList.size();
    }


}

Person.java

public class Person {

    private Uri mImage;
    private String mName, mAge;

    //constructor
    public Person(Uri mImage, String mName, String mAge) {
        this.mImage = mImage;
        this.mName = mName;
        this.mAge = mAge;
    }

    //getters and setters
    public Uri getmImage() {
        return mImage;
    }

    public void setmImage(Uri mImage) {
        this.mImage = mImage;
    }

    public String getmName() {
        return mName;
    }

    public void setmName(String mName) {
        this.mName = mName;
    }

    public String getmAge() {
        return mAge;
    }

    public void setmAge(String mAge) {
        this.mAge = mAge;
    }
}

Logcat

2019-07-21 16:06:59.623 4287-4287/com.example.recyclerviewobject E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.recyclerviewobject, PID: 4287
    java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=0, result=-1, data=Intent { (has extras) }} to activity {com.example.recyclerviewobject/com.example.recyclerviewobject.MainActivity}: java.lang.IllegalArgumentException: No suitable parent found from the given view. Please provide a valid view.
        at android.app.ActivityThread.deliverResults(ActivityThread.java:4932)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:4975)
        at android.app.ActivityThread.-wrap20(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1950)
        at android.os.Handler.dispatchMessage(Handler.java:108)
        at android.os.Looper.loop(Looper.java:166)
        at android.app.ActivityThread.main(ActivityThread.java:7425)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)
     Caused by: java.lang.IllegalArgumentException: No suitable parent found from the given view. Please provide a valid view.
        at android.support.design.widget.Snackbar.make(Snackbar.java:181)
        at com.example.recyclerviewobject.MainActivity.onActivityResult(MainActivity.java:91)
        at android.app.Activity.dispatchActivityResult(Activity.java:7690)
        at android.app.ActivityThread.deliverResults(ActivityThread.java:4928)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:4975) 
        at android.app.ActivityThread.-wrap20(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1950) 
        at android.os.Handler.dispatchMessage(Handler.java:108) 
        at android.os.Looper.loop(Looper.java:166) 
        at android.app.ActivityThread.main(ActivityThread.java:7425) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)

【问题讨论】：

如果您的应用突然关闭并且您使用的是 Android Pie，那就是崩溃。尝试重复您的步骤，您将在 LogCat 中看到堆栈跟踪。请在此处粘贴堆栈跟踪
@Skullper 哎呀我忘了，我更新了我的帖子并添加了 logcat
作为@a_local_nobody，你的协调器没有被findViewById()初始化。这就是你在 onActivityResult 方法中崩溃的原因。尝试 inti 让我们知道发生了什么

标签： android android-recyclerview

【解决方案1】：

尝试删除这个：

mRecyclerView = (RecyclerView) findViewById(R.id.recyclerview);
mAdapter = new PersonAdapter(personArrayList);
mAdapter.notifyDataSetChanged();
mRecyclerView.setAdapter(mAdapter);

还有

private CoordinatorLayout coordinatorLayout;

从未使用findViewById(); 初始化然后您的 snackbar 代码可能失败，因为您传递的布局 (coordinatorLayout) 为空

【讨论】：