android GridView实现图库预览图，多选模式下右上角打勾

看到有初学者有这样的需求： GridView实现图库预览图，多选模式下右上角打勾。（4.0图库的预览图多选时，多了个蓝色边框，其实是蓝色背景）

       GridView在自己实际开发中也没用到过，就想试着实现下，写个demo供初学者参考,高手略过。

       先来个效果图吧：

       实现起来不复杂，就2个文件。 首先看看GridView继承关系：

       

java.lang.Object
↳	android.view.View
	↳	android.view.ViewGroup
		↳	android.widget.AdapterView
			↳	android.widget.AbsListView
				↳	android.widget.GridView

     我们知道ListView有单选模式和多选模式[AbsListView.setChoiceMode(AbsListView.CHOICE_MODE_SINGLE/AbsListView.CHOICE_MODE_MULTIPLE_MODAL)]

     那么GridView也支持多选模式。

     废话不多说，相信你也知道！贴代码吧

主布局文件：main.xml

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

     <GridView
         android:id="@+id/gridview"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:columnWidth="75dip"
         android:gravity="center"
         android:horizontalSpacing="2dip"
         android:numColumns="4"
         android:verticalSpacing="2dip" />

 LinearLayout>

主Activity：HomeActivity

 package com.xyz.gridview;

 import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;

 import android.app.Activity;
 import android.content.Context;
 import android.os.Bundle;
 import android.view.ActionMode;
 import android.view.LayoutInflater;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.AbsListView.LayoutParams;
 import android.widget.AbsListView.MultiChoiceModeListener;
 import android.widget.BaseAdapter;
 import android.widget.Checkable;
 import android.widget.FrameLayout;
 import android.widget.GridView;
 import android.widget.ImageView;
 import android.widget.ListAdapter;
 import android.widget.TextView;

 public class HomeActivity extends Activity implements MultiChoiceModeListener {

     private GridView mGridView;
     private GridAdapter mGridAdapter;
     private TextView mActionText;
     private static final int MENU_SELECT_ALL = 0;
     private static final int MENU_UNSELECT_ALL = MENU_SELECT_ALL + 1;
     private Map mSelectMap = new HashMap();

     private int[] mImgIds = new int[] { R.drawable.img_1, R.drawable.img_2,
             R.drawable.img_3, R.drawable.img_4, R.drawable.img_5,
             R.drawable.img_6, R.drawable.img_7, R.drawable.img_8,
             R.drawable.img_9, R.drawable.img_1, R.drawable.img_2,
             R.drawable.img_3, R.drawable.img_4, R.drawable.img_5,
             R.drawable.img_6, R.drawable.img_7 };

     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);

         mGridView = (GridView) findViewById(R.id.gridview);
         mGridView.setChoiceMode(GridView.CHOICE_MODE_MULTIPLE_MODAL);
         mGridAdapter = new GridAdapter(this);
         mGridView.setAdapter(mGridAdapter);
         mGridView.setMultiChoiceModeListener(this);
     }

     /** Override MultiChoiceModeListener start **/
     @Override
     public boolean onCreateActionMode(ActionMode mode, Menu menu) {
         // TODO Auto-generated method stub
         View v = LayoutInflater.from(this).inflate(R.layout.actionbar_layout,
                 null);
         mActionText = (TextView) v.findViewById(R.id.action_text);
         mActionText.setText(formatString(mGridView.getCheckedItemCount()));
         mode.setCustomView(v);
         getMenuInflater().inflate(R.menu.action_menu, menu);
         return true;
     }

     @Override
     public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
         // TODO Auto-generated method stub
         menu.getItem(MENU_SELECT_ALL).setEnabled(
                 mGridView.getCheckedItemCount() != mGridView.getCount());
         return true;
     }

     @Override
     public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
         // TODO Auto-generated method stub
         switch (item.getItemId()) {
         case R.id.menu_select:
             for (int i = 0; i < mGridView.getCount(); i++) {
                 mGridView.setItemChecked(i, true);
                 mSelectMap.put(i, true);
             }
             break;
         case R.id.menu_unselect:
             for (int i = 0; i < mGridView.getCount(); i++) {
                 mGridView.setItemChecked(i, false);
             }
             mSelectMap.clear();
             break;
         }
         return true;
     }

     @Override
     public void onDestroyActionMode(ActionMode mode) {
         // TODO Auto-generated method stub
         mGridAdapter.notifyDataSetChanged();
     }

     @Override
     public void onItemCheckedStateChanged(ActionMode mode, int position,
             long id, boolean checked) {
         // TODO Auto-generated method stub
         mActionText.setText(formatString(mGridView.getCheckedItemCount()));
         mSelectMap.put(position, checked);
         mode.invalidate();
     }

     /** Override MultiChoiceModeListener end **/

     private String formatString(int count) {
         return String.format(getString(R.string.selection), count);
     }

     private class GridAdapter extends BaseAdapter {

         private Context mContext;

         public GridAdapter(Context ctx) {
             mContext = ctx;
         }

         @Override
         public int getCount() {
             // TODO Auto-generated method stub
             return mImgIds.length;
         }

         @Override
         public Integer getItem(int position) {
             // TODO Auto-generated method stub
             return Integer.valueOf(mImgIds[position]);
         }

         @Override
         public long getItemId(int position) {
             // TODO Auto-generated method stub
             return position;
         }

         @Override
         public View getView(int position, View convertView, ViewGroup parent) {
             // TODO Auto-generated method stub
             GridItem item;
             if (convertView == null) {
                 item = new GridItem(mContext);
                 item.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,
                         LayoutParams.FILL_PARENT));
             } else {
                 item = (GridItem) convertView;
             }
             item.setImgResId(getItem(position));
             item.setChecked(mSelectMap.get(position) == null ? false
                     : mSelectMap.get(position));
             return item;
         }
     }

 }

 

     上面用到 GridItem是自己封装的一个类：GridItem.java

 package com.xyz.gridview;

 import android.content.Context;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.widget.Checkable;
 import android.widget.ImageView;
 import android.widget.RelativeLayout;

 public class GridItem extends RelativeLayout implements Checkable {

     private Context mContext;
     private boolean mChecked;
     private ImageView mImgView = null;
     private ImageView mSelcetView = null;

     public GridItem(Context context) {
         this(context, null, 0);
     }

     public GridItem(Context context, AttributeSet attrs) {
         this(context, attrs, 0);
     }

     public GridItem(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
         // TODO Auto-generated constructor stub
         mContext = context;
         LayoutInflater.from(mContext).inflate(R.layout.grid_item, this);
         mImgView = (ImageView) findViewById(R.id.img_view);
         mSelcetView = (ImageView) findViewById(R.id.select);
     }

     @Override
     public void setChecked(boolean checked) {
         // TODO Auto-generated method stub
         mChecked = checked;
         setBackgroundDrawable(checked ? getResources().getDrawable(
                 R.drawable.background) : null);
         mSelcetView.setVisibility(checked ? View.VISIBLE : View.GONE);
     }

     @Override
     public boolean isChecked() {
         // TODO Auto-generated method stub
         return mChecked;
     }

     @Override
     public void toggle() {
         // TODO Auto-generated method stub
         setChecked(!mChecked);
     }

     public void setImgResId(int resId) {
         if (mImgView != null) {
             mImgView.setBackgroundResource(resId);
         }
     }

 }

    这个类引用的一个布局：grid_item.xml

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

     <ImageView
         android:id="@+id/img_view"
         android:layout_width="fill_parent"
         android:layout_height="fill_parent"
         android:scaleType="fitXY" />

     <ImageView
         android:id="@+id/select"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentRight="true"
         android:layout_alignParentTop="true"
         android:background="@drawable/icon_choice"
         android:visibility="gone" />

 RelativeLayout>

     就这么多啦。左上角的勾，就是控制 ImageView 显示与不显示的问题。

     源码路径：http://download.csdn.net/detail/zhouyuanjing/4916510

    转自：http://blog.csdn.net/zhouyuanjing/article/details/8372686 感谢作者