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<T extends android.widget.Adapter>
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
[html]
<?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
[java]
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;
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<Integer, Boolean> mSelectMap = new HashMap<Integer, Boolean>();
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); www.2cto.com
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
[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 mSecletView = 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);
mSecletView = (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);
mSecletView.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
[html]
<?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>
