在Android中使用数据绑定的RecyclerView无法正常工作

Question

I am trying to implement data binding with RecyclerView in Android but it doesn't display properly. If i give list of 4 items then it shows only 3 items in RecyclerView . It doesn't display item of 0th index.

FileListActivity.java

package com.example.vipul.databindingdemo;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;

import com.example.kush.MyAdapter;
import com.example.kush.SimpleDividerItemDecoration;
import com.example.kush.TemperatureData;

import java.util.Arrays;
import java.util.List;

public class FileListActivity extends AppCompatActivity {
    private RecyclerView recyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_file_list);
        recyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);

        // use this setting to improve performance if you know that changes
        // in content do not change the layout size of the RecyclerView
        recyclerView.setHasFixedSize(true);

        // use a linear layout manager
        mLayoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(mLayoutManager);
        recyclerView.addItemDecoration(new SimpleDividerItemDecoration(this));

        List<TemperatureData> items =
                Arrays.asList(new TemperatureData("Hamburg", "5"), new TemperatureData("Berlin", "6"), new TemperatureData("Ahmedabad", "36"), new TemperatureData("Mumbai", "26"));

        // define an adapter
        mAdapter = new MyAdapter(items);
        recyclerView.setAdapter(mAdapter);
    }

}

Here is a Model Class.

TemperatureData.java

package com.example.kush;

import android.databinding.BaseObservable;
import android.databinding.Bindable;

import com.example.vipul.databindingdemo.BR;

/**
 * Created by kushpatel on 8/2/2017.
 */

public class TemperatureData extends BaseObservable {
    private String location;
    private String celsius;

    public TemperatureData(String location, String celsius) {
        this.location = location;
        this.celsius = celsius;
    }

    @Bindable
    public String getCelsius() {
        return celsius;
    }

    @Bindable
    public String getLocation() {
        return location;
    }

    public  void setLocation(String location){
        this.location = location;
        notifyPropertyChanged(BR.location);
    }

    public void setCelsius(String celsius) {
        this.celsius = celsius;
        notifyPropertyChanged(BR.celsius);
    }

}

Here is an Adapter for RecyclerView.

MyAdapter.java

package com.example.kush;

import android.databinding.DataBindingUtil;
import android.databinding.ViewDataBinding;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.ViewGroup;

import com.example.vipul.databindingdemo.BR;
import com.example.vipul.databindingdemo.R;

import java.util.List;

/**
 * Created by kushpatel on 8/2/2017.
 */

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
    private List<TemperatureData> data;

    // Provide a reference to the views for each data item
    // Complex data items may need more than one view per item, and
    // you provide access to all the views for a data item in a view holder
    public class MyViewHolder extends RecyclerView.ViewHolder {
        // each data item is just a string in this case
        private final ViewDataBinding binding;

        public MyViewHolder(ViewDataBinding binding) {
            super(binding.getRoot());
            this.binding = binding;
        }
        public void bind(Object obj) {
            binding.setVariable(BR.obj,obj);
            binding.executePendingBindings();
        }
    }

    // Provide a suitable constructor (depends on the kind of dataset)
    public MyAdapter(List<TemperatureData> myDataset) {
        data = myDataset;
    }

    // Create new views (invoked by the layout manager)
    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        // create a new view
        LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
        ViewDataBinding binding = DataBindingUtil.inflate(layoutInflater, R.layout.rawlayout, parent, false);
        // set the view's size, margins, paddings and layout parameters
        return new MyViewHolder(binding);
    }

    // Replace the contents of a view (invoked by the layout manager)
    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        final TemperatureData temperatureData = data.get(position);
        holder.bind(temperatureData);

    }

    // Return the size of your dataset (invoked by the layout manager)
    @Override
    public int getItemCount() {
        return data.size();
    }

}

Layout for row of RecyclerView

rawlayout.xml

<layout xmlns:android="http://schemas.android.com/apk/res/android">

    <data>

        <variable
            name="obj"
            type="com.example.kush.TemperatureData"
            />
    </data>

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="?android:attr/listPreferredItemHeight"
        android:padding="6dip"
        >

        <ImageView
            android:id="@+id/icon"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_alignParentBottom="true"
            android:layout_alignParentTop="true"
            android:layout_marginRight="6dip"
            android:contentDescription="TODO"
            android:src="@android:drawable/arrow_down_float"
            />

        <TextView
            android:id="@+id/secondLine"
            android:layout_width="fill_parent"
            android:layout_height="26dip"
            android:layout_alignParentBottom="true"
            android:layout_alignParentRight="true"
            android:layout_toRightOf="@id/icon"
            android:ellipsize="marquee"
            android:text="@{obj.location}"
            android:textSize="12sp"
            android:maxLines="1"
            />

        <TextView
            android:id="@+id/firstLine"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_above="@id/secondLine"
            android:layout_alignParentRight="true"
            android:layout_alignParentTop="true"
            android:layout_alignWithParentIfMissing="true"
            android:layout_toRightOf="@id/icon"
            android:gravity="center_vertical"
            android:text="@{obj.celsius}"
            android:textSize="16sp"
            />

    </RelativeLayout>

</layout>

Answer 1

Your first element is not visible, I should be hidden behind the toolbar. please add the margin 50dp or equal to your action bar/toolbar size.

  android:layout_marginTop="?android:attr/actionBarSize"