Android常用控件之GridView的蒙板用途和写法

内容

GridView常用语显示照片墙，例如上传图片时当选中一个图片时，会出现一些特殊效果，此时要用到checkBox和蒙板。
布局文件，必须将GridView放在RelativeLayout或FrameLayout，此处用的是最常用的RelativeLayout

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"                xmlns:tools="http://schemas.android.com/tools"                android:layout_width="match_parent"                android:layout_height="match_parent"                android:orientation="vertical">    <GridView        android:id="@+id/grid_view"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_margin="10dp"        android:numColumns="3">    </GridView></LinearLayout>

GridView的单元项布局grid_item,其中我的蒙板的写法是用一个ImageView设置背景覆盖其他控件，背景默认不显示

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"                android:layout_width="match_parent"                android:layout_height="match_parent"                android:layout_margin="5dp">    <CheckBox        android:id="@+id/item_checkbox"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentRight="true"/>    <ImageView        android:id="@+id/item_imageview"        android:layout_width="100dp"        android:layout_height="100dp"        android:layout_below="@+id/item_checkbox"        android:layout_centerHorizontal="true"        android:src="@mipmap/pk"/>    <TextView        android:id="@+id/item_textview"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_below="@+id/item_imageview"        android:layout_centerHorizontal="true"        android:gravity="center"        android:text="pingguo"/>    <ImageView        android:id="@+id/item_image_tint"        android:layout_width="165dp"        android:layout_height="150dp"        android:layout_alignLeft="@+id/item_imageview"        android:layout_alignTop="@+id/item_checkbox"        android:background="#55ff0000"        android:visibility="invisible"/></RelativeLayout>

接着建立一个存放单元信息的类Fruit()，其实并不是水果，此处请无视

public class Fruit {    private String name;    private int img;    public Fruit(String name, int img) {        this.name = name;        this.img = img;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getImg() {        return img;    }    public void setImg(int img) {        this.img = img;    }}

接着建立一个自定义适配器

public class FruitGridAdapter extends BaseAdapter {    private List<Fruit> mFruits;    private LayoutInflater mInflater;    //mCheckBoxManager用于存储所有checkBox是否被选中的状态    private boolean[] mCheckBoxManager;    public FruitGridAdapter(List<Fruit> mFruits, LayoutInflater mInflater) {        this.mFruits = mFruits;        this.mInflater = mInflater;        mCheckBoxManager = new boolean[mFruits.size()];    }    @Override    public int getCount() {        return mFruits.size();    }    @Override    public Object getItem(int position) {        return position;    }    @Override    public long getItemId(int position) {        return position;    }    @Override    public View getView(final int position, View convertView, ViewGroup parent) {        final ViewHolder viewHolder;        if(convertView==null){            viewHolder = new ViewHolder();            convertView = mInflater.inflate(R.layout.grid_item,null);            viewHolder.imageView = (ImageView) convertView.findViewById(R.id.item_imageview);            viewHolder.textView = (TextView) convertView.findViewById(R.id.item_textview);            viewHolder.checkBox = (CheckBox)convertView.findViewById(R.id.item_checkbox);            viewHolder.tintImageView = (ImageView)convertView.findViewById(R.id.item_image_tint);            convertView.setTag(viewHolder);        }else{            viewHolder = (ViewHolder) convertView.getTag();        }        Fruit fruit = mFruits.get(position);        viewHolder.imageView.setImageResource(fruit.getImg());        viewHolder.textView.setText(fruit.getName());        viewHolder.checkBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {            @Override            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {                mCheckBoxManager[position] = isChecked;                notifyDataSetChanged();//刷新界面信息            }        });        viewHolder.checkBox.setChecked(mCheckBoxManager[position]);        //如果一个图片对应的checkBox被选中，则让该图的蒙板可见，否则设置为不可见。        if(mCheckBoxManager[position]){            viewHolder.tintImageView.setVisibility(View.VISIBLE);        }else{            viewHolder.tintImageView.setVisibility(View.INVISIBLE);        }        return convertView;    }    class ViewHolder{        ImageView imageView;        TextView textView;        CheckBox checkBox;        ImageView tintImageView;    }}

主活动

public class MainActivity extends Activity {    private List<Fruit> mFruits;    private LayoutInflater mInflater;    private GridView gridView;    private FruitGridAdapter mAdapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        gridView = (GridView) findViewById(R.id.grid_view);        mInflater = this.getLayoutInflater();        mFruits = new ArrayList<>();        Fruit apple = new Fruit("apple", R.mipmap.a_logo1);        Fruit pear = new Fruit("pear", R.mipmap.image);        Fruit pineapple = new Fruit("pineapple", R.mipmap.pk);        Fruit grape = new Fruit("grape", R.mipmap.ic_launcher);        for (int i = 0; i < 20; i++) {            mFruits.add(apple);            mFruits.add(pear);            mFruits.add(pineapple);            mFruits.add(grape);        }        mAdapter = new FruitGridAdapter(mFruits,mInflater);        gridView.setAdapter(mAdapter);    }}

结果演示：