java - 图像未显示在 Android Studio 设计选项卡上的网格布局中

Question

您好，我在 Gridlayout 的 imageview 中添加了一个图像，但它没有显示在设计 View 中，但它在实际设备上是可见的。我的代码是..

<android.support.v7.widget.GridLayout
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginBottom="86dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="138dp"
        android:background="@drawable/board"
        app:columnCount="3"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:rowCount="3">

        <ImageView
            android:id="@+id/imageView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="10dp"
            app:srcCompat="@drawable/red" />

    </android.support.v7.widget.GridLayout>

Desing tab screenshot

App on Actual devicestrong text

Answer 1

您无法从 xml 静态地将 ImageView 添加到 Gridview 中。

使用GridView，需要编写一个Adapter(其名称为BasicAdapter、ArrayAdapter、Listadapter等)。每个适配器都有一个名为“getView(View view, View Parent, args)”的函数，只需覆盖它并返回您想要在 GridView 中拥有的 View 。

Here is xml for GridView

<GridView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/gridview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:columnWidth="90dp"
android:numColumns="auto_fit"
android:verticalSpacing="10dp"
android:horizontalSpacing="10dp"
android:stretchMode="columnWidth"
android:gravity="center"/>

Here is the view attachment and item Click of GridView

public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

GridView gridview = (GridView) findViewById(R.id.gridview);
gridview.setAdapter(new ImageAdapter(this));

gridview.setOnItemClickListener(new OnItemClickListener() {
    public void onItemClick(AdapterView<?> parent, View v,
            int position, long id) {
        Toast.makeText(HelloGridView.this, "" + position,
                Toast.LENGTH_SHORT).show();
    }
});

}

Here is Custom Base Adapter for adding custom views in GridView.

public class ImageAdapter extends BaseAdapter {
private Context mContext;

public ImageAdapter(Context c) {
    mContext = c;
}

public int getCount() {
    return mThumbIds.length;
}

public Object getItem(int position) {
    return null;
}

public long getItemId(int position) {
    return 0;
}

// create a new ImageView for each item referenced by the Adapter
public View getView(int position, View convertView, ViewGroup parent) {
    ImageView imageView;
    if (convertView == null) {
        // if it's not recycled, initialize some attributes
        imageView = new ImageView(mContext);
        imageView.setLayoutParams(new ViewGroup.LayoutParams(85, 85));
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        imageView.setPadding(8, 8, 8, 8);
    } else {
        imageView = (ImageView) convertView;
    }

    imageView.setImageResource(mThumbIds[position]);
    return imageView;
}

// references to our images
private Integer[] mThumbIds = {
        R.drawable.sample_2, R.drawable.sample_3,
        R.drawable.sample_4, R.drawable.sample_5,
        R.drawable.sample_6, R.drawable.sample_7,
        R.drawable.sample_0, R.drawable.sample_1,
        R.drawable.sample_2, R.drawable.sample_3,
        R.drawable.sample_4, R.drawable.sample_5,
        R.drawable.sample_6, R.drawable.sample_7,
        R.drawable.sample_0, R.drawable.sample_1,
        R.drawable.sample_2, R.drawable.sample_3,
        R.drawable.sample_4, R.drawable.sample_5,
        R.drawable.sample_6, R.drawable.sample_7
};}