ListView CustomAdapter 不显示首位结果

Question

我是 Android Studio 和一般编码的新手，我正在尝试显示带有颜色图像和颜色名称的自定义 ListView。我使用自定义适配器通过两个包含可绘制图像颜色和名称字符串的数组来膨胀视图。

我遇到的问题 - 自定义适配器只显示从位置 1 开始的图层。例如，第一层应该是 img_01 和 "red" - 它显示 img_02 和 "Orange"。

我试过调试代码，似乎虽然适配器正在为位置 0 设置值，但我找不到它不显示的原因（因为其他显示正常）。

图像和名称只是占位符，因此不包含可绘制对象和名称的替代解决方案不可行，

提前致谢

CustomAdapter.java

public class CustomAdapter extends BaseAdapter {

    Context context;
    int[] images;
    String[] colour;
    LayoutInflater mInflater;

    public CustomAdapter(Context c, int[] i, String[] col) {
        this.context = c; //sets the application context that has been passed to the adapter
        this.images = i; //sets the images array that has been passed to the adapter
        this.colour = col; //sets the colour array that has been passed to the adapter
        mInflater = (LayoutInflater.from(context)); //sets the layout inflater from context
    }

    @Override
    public int getCount() { //total number of elements in the array
        return images.length;
    }

    @Override
    public Object getItem(int position) { //gets the item using the position
        return null;
    }

    @Override
    public long getItemId(int position) { //gets the item position
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) { //this is used to update the view

        convertView = mInflater.inflate(R.layout.custom_layout, null);

        ImageView image = convertView.findViewById(R.id.imageView);

        TextView text = convertView.findViewById(R.id.textView);

        text.setText(colour[position]);
        image.setImageResource(images[position]);
        return convertView;

    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

    ListView mListView;

    int[] images = {R.drawable.img01,
    R.drawable.img02,
    R.drawable.img03,
    R.drawable.img04};

    String[] colour = {"Red",
    "Orange",
    "Yellow",
    "Green"};

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

        mListView = findViewById(R.id.listView);

        CustomAdapter customAdapter = new CustomAdapter(getApplicationContext(), images, colour);
        //passes information of images and application context to the item adapter
        mListView.setAdapter(customAdapter);
        //sets the adapter to the listview

    }
}

custom_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent" android:layout_height="match_parent">


    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginStart="7dp"
        android:layout_marginLeft="7dp"
        android:layout_marginTop="9dp"
        app:srcCompat="@drawable/img01" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginStart="99dp"
        android:layout_marginLeft="99dp"
        android:layout_marginTop="36dp"
        android:text="colourName" />

</RelativeLayout>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <ListView
        android:id="@+id/listView"
        android:layout_width="409dp"
        android:layout_height="729dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

你可以用 RecyclerView 做到这一点。

创建自定义 class

public class ExampleItem {
    private int mImageResource; //your color image
    private String mText1; //your text

    public ExampleItem(int imageResource, String text1) {
        mImageResource = imageResource;
        mText1 = text1;
    }
    public int getImageResource() {
        return mImageResource;
    }
    public String getText1() {
        return mText1;
    }
}

创建 XML 布局

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginBottom="4dp"
    app:cardCornerRadius="4dp">
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_margin="4dp">
        <ImageView
            android:id="@+id/imageView"
            android:layout_width="50dp"
            android:layout_height="50dp"
            android:padding="2dp" />
        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_toEndOf="@+id/imageView"
            android:text="Line 1"
            android:textColor="@android:color/black"
            android:textSize="20sp"
            android:textStyle="bold" />
    </RelativeLayout>
</android.support.v7.widget.CardView>

创建一个 Recycler 视图适配器

public class ExampleAdapter extends RecyclerView.Adapter<ExampleAdapter.ExampleViewHolder> {
    private ArrayList<ExampleItem> mExampleList;
    public static class ExampleViewHolder extends RecyclerView.ViewHolder {
        public ImageView mImageView;
        public TextView mTextView1;

        public ExampleViewHolder(View itemView) {
            super(itemView);
            mImageView = itemView.findViewById(R.id.imageView);
            mTextView1 = itemView.findViewById(R.id.textView);
        }
    }
    public ExampleAdapter(ArrayList<ExampleItem> exampleList) {
        mExampleList = exampleList;
    }
    @Override
    public ExampleViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.example_item, parent, false);
        ExampleViewHolder evh = new ExampleViewHolder(v);
        return evh;
    }
    @Override
    public void onBindViewHolder(ExampleViewHolder holder, int position) {
        ExampleItem currentItem = mExampleList.get(position);
        holder.mImageView.setImageResource(currentItem.getImageResource());
        holder.mTextView1.setText(currentItem.getText1());
    }
    @Override
    public int getItemCount() {
        return mExampleList.size();
    }
}

你的activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.application.recyclerviewproject.MainActivity">
    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@android:color/darker_gray"
        android:padding="4dp"
        android:scrollbars="vertical" />
</RelativeLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity {
    private RecyclerView mRecyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ArrayList<ExampleItem> exampleList = new ArrayList<>();
        exampleList.add(new ExampleItem(R.drawable.img01, "Red"));
        exampleList.add(new ExampleItem(R.drawable.img02, "Orange"));
        exampleList.add(new ExampleItem(R.drawable.img03, "Yellow"));
        exampleList.add(new ExampleItem(R.drawable.img04, "Green"));

        mRecyclerView = findViewById(R.id.recyclerView);
        mRecyclerView.setHasFixedSize(true);
        mLayoutManager = new LinearLayoutManager(this);
        mAdapter = new ExampleAdapter(exampleList);
        mRecyclerView.setLayoutManager(mLayoutManager);
        mRecyclerView.setAdapter(mAdapter);
    }
}

Answer 2

尝试将 ListView 的高度设置为 wrap_content 而不是硬编码

<ListView
    ...
    android:layout_height="wrap_content"/>

ListView CustomAdapter 不显示首位结果

ListView CustomAdapter not showing first position results

java

android

listview

custom-adapter