Android_GridView

Android_GridView

　　gridview与listview大同小异,gridview呈现的是九宫格的布局,listview呈现的是列表布局

gridview的一些特殊属性:

1.android:numColumns=”auto_fit”   //GridView的列数设置为自动

2.android:columnWidth=”90dp "       //每列的宽度，也就是Item的宽度

3.android:stretchMode=”columnWidth"//缩放与列宽大小同步

4.android:verticalSpacing=”10dp”          //两行之间的边距

5.android:horizontalSpacing=”10dp”      //两列之间的边距 

6.android:cacheColorHint="#00000000" //去除拖动时默认的黑色背景

7.android:listSelector="#00000000"        //去除选中时的黄色底色

8.android:scrollbars="none"                   //隐藏GridView的滚动条

9.android:fadeScrollbars="true"             //设置为true就可以实现滚动条的自动隐藏和显示

10.android:fastScrollEnabled="true"      //GridView出现快速滚动的按钮(至少滚动4页才会显示)

11.android:fadingEdge="none"                //GridView衰落(褪去)边缘颜色为空，缺省值是vertical。(可以理解为上下边缘的提示色)

12.android:fadingEdgeLength="10dip"   //定义的衰落(褪去)边缘的长度

13.android:stackFromBottom="true"       //设置为true时，你做好的列表就会显示你列表的最下面

14.android:transcriptMode="alwaysScroll" //当你动态添加数据时，列表将自动往下滚动最新的条目可以自动滚动到可视范围内

15.android:drawSelectorOnTop="false"  //点击某条记录不放，颜色会在记录的后面成为背景色,内容的文字可见(缺省为false)

 Demo环节:

一般步骤:gridview布局  --> item布局 -->数据源-->   适配器(将数据与item绑定)  --> 为gridview添加适配器

使用gridview加载网络图片:

主布局xml:

<?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">
 <GridView
     android:id="@+id/one_gradView"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:columnWidth="70dp"
     android:numColumns="auto_fit"
     android:verticalSpacing="20dp"
     android:horizontalSpacing="20dp"
     android:stretchMode="columnWidth"
     android:gravity="center"/>
</RelativeLayout>

 item布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:orientation="vertical"
    >
    <ImageView
        android:id="@+id/three_img"
        android:layout_width="150dp"
        android:layout_height="150dp" />
</LinearLayout>

数据源:通过异步下载图片获取数据

 //网络图片地址
    private void initData() {
        imgList = new ArrayList<>();
        imgList.add("http://img5.duitang.com/uploads/item/201406/26/20140626164837_dzKds.jpeg");
        imgList.add("http://img2.imgtn.bdimg.com/it/u=3980629563,3881837630&fm=21&gp=0.jpg");
        imgList.add("http://img5q.duitang.com/uploads/item/201505/08/20150508155052_XJaNW.jpeg");
        imgList.add("http://img4.duitang.com/uploads/item/201407/02/20140702105736_FdN5P.jpeg");
        imgList.add("http://img2.imgtn.bdimg.com/it/u=2866652161,3841912673&fm=21&gp=0.jpg");
        imgList.add("http://img4.imgtn.bdimg.com/it/u=883757693,2063816225&fm=21&gp=0.jpg");
        imgList.add("http://cdn.duitang.com/uploads/item/201309/26/20130926110955_QtUdX.jpeg");
        imgList.add("http://zjimg.5054399.com/allimg/160815/14_160815161625_9.jpg");
        imgList.add("http://i-7.vcimg.com/trim/09ce7067d2467c54cf05bbd271ee3ec8430415/trim.jpg");

    }
    //下载网络图片
    public Bitmap downImg(String urlPath){

        try {
            URL url = new URL(urlPath);
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setConnectTimeout(6000);
            urlConnection.setDoInput(true);
            urlConnection.connect();
            InputStream inputStream = urlConnection.getInputStream();
            Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
            inputStream.close();
            return bitmap;
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }





    //创建AsycnTask加载图片
    public class MyAsycnTask extends AsyncTask<String,String,String>{
        ThreeAdapter threeAdapter;

        public MyAsycnTask(ThreeAdapter threeAdapter) {
            this.threeAdapter = threeAdapter;
        }

        @Override
        protected String doInBackground(String... strings) {
            for (int i = 0; i <imgList.size() ; i++) {
                bitmapList.add(downImg(imgList.get(i)));
                publishProgress();
            }
            return null;
        }

        @Override
        protected void onProgressUpdate(String... values) {
            super.onProgressUpdate(values);
            //通知适配器更新数据
            threeAdapter.notifyDataSetChanged();
        }
    }

适配器:

public class ThreeAdapter extends BaseAdapter {
    private Context context;

    private List<Bitmap> bitmapList;
    public ThreeAdapter(Context context,List<Bitmap> bitmapList1) {
        this.context = context;
        this.bitmapList = bitmapList1;
    }
    @Override
    public int getCount() {
        return bitmapList.size();
    }

    @Override
    public Object getItem(int i) {
        return bitmapList.get(i);
    }

    @Override
    public long getItemId(int i) {
        return i;
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        viewHodler viewHodler = null;
        if (view == null){
            view = View.inflate(context, R.layout.three_item,null);
            viewHodler = new viewHodler();
            viewHodler.imageView = view.findViewById(R.id.three_img);
            view.setTag(viewHodler);
        }else {
            viewHodler = (ThreeAdapter.viewHodler) view.getTag();
        }
        //如果图片无法加载则显示默认图片
        if (bitmapList.get(i) == null)
        {
            viewHodler.imageView.setImageResource(R.drawable.ic_launcher_background);
        }else {
            viewHodler.imageView.setImageBitmap(bitmapList.get(i));
        }

        return view;
    }
    //辅助类,优化缓存
    public class viewHodler{
        ImageView imageView;
    }
}

主要实现

public class ThreeActivity extends AppCompatActivity {
    private List<Bitmap> bitmapList;//存放图片
    protected List<String> imgList;//存放图片网络地址
    protected GridView gridView;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.second_layout);
        gridView = findViewById(R.id.scond_graidView);
        bitmapList = new ArrayList<>(10);
        initData();
        ThreeAdapter threeAdapter = new ThreeAdapter(this, bitmapList);
        MyAsycnTask myAsycnTask = new MyAsycnTask(threeAdapter);
        myAsycnTask.execute();
        gridView.setAdapter(threeAdapter);

    }
}

获取系统应用信息:

自定义应用信息类AppInfo:

/**
 * 获取应用信息类
 */
public class AppInfo {
    //应用名称
    private String appName;
    //应用包名
    private String packgeName;
    //版本名称
    private String versionName;
    //版本号
    private int versionCode;
    //应用图标
    private Drawable appIcon;

    public String getAppName() {
        return appName;
    }

    public void setAppName(String appName) {
        this.appName = appName;
    }

    public String getPackgeName() {
        return packgeName;
    }

    public void setPackgeName(String packgeName) {
        this.packgeName = packgeName;
    }

    public String getVersionName() {
        return versionName;
    }

    public void setVersionName(String versionName) {
        this.versionName = versionName;
    }

    public int getVersionCode() {
        return versionCode;
    }

    public void setVersionCode(int versionCode) {
        this.versionCode = versionCode;
    }

    public Drawable getAppIcon() {
        return appIcon;
    }

    public void setAppIcon(Drawable appIcon) {
        this.appIcon = appIcon;
    }
}

获取应用信息方法:

 /**
     * 获取app信息方法
     */
    public List<AppInfo> getAppList(){
        List<AppInfo> list  = new ArrayList<>();
        //获取包管理器
        PackageManager packageManager = getPackageManager();
        //获取包信息集合
        List<PackageInfo> installedPackages = packageManager.getInstalledPackages(0);

        for (int i = 0; i <installedPackages.size() ; i++) {
            PackageInfo packageInfo = installedPackages.get(i);
            //实例化AppInfo
            AppInfo appInfo = new AppInfo();
            //获取应用名称
            appInfo.setAppName(packageInfo.applicationInfo.loadLabel(packageManager).toString());
            //获取应用图标
            appInfo.setAppIcon(packageInfo.applicationInfo.loadIcon(packageManager));
            //获取包名
            appInfo.setPackgeName(packageInfo.packageName);
            //获取版本号
            appInfo.setVersionCode(packageInfo.versionCode);
            //获取版本名称
            appInfo.setVersionName(packageInfo.versionName);
            //判断是否为用户自定义安装程序
            if ((packageInfo.applicationInfo.flags&ApplicationInfo.FLAG_SYSTEM) == 0){
                list.add(appInfo);
            }
        }
        return list;
    }

 总体来说gridview的用法与listview差不多,创建布局,获取数据源,通过适配器将数据源与布局绑定在显示在页面上