android控件大全及用法_学双人舞一步一步教学

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GridView 用于显示二维滚动网格的View。同ListView一样，他的数据项也是从ListAdapter中产生。关于他的使用方法可参见官网的示例GridView 。

下面先了解下GridView中常用到的属性：

1、android:numColumn : 指定GridView的列数，如果指定为auto_fit ，则可能根据控件的大小自动调整每行显示的列数。

2、android:strechMode : 伸缩模式，值为none （不可伸缩）、 spacingWidth（伸缩列之间的间隔空隙）、 columnWidth（每列伸缩大小一样）、 spacingWidthUniform（均匀拉伸各列之间的距离）。

3、 android:columnWidth : 指定列宽度。

关于GridView属性的介绍就到这里。今天通过做一个类似于launcher功能的小程序来学习GridView。先看看程序效果：

android控件大全及用法_学双人舞一步一步教学

下面一步一步实现该功能：

1、activity使用的布局文件，文中指定显示3列。widget_gridview_layout.xml

<?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" >

    <GridView
        android:id="@+id/show_app_grid_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:numColumns="3"
        android:smoothScrollbar="true"
        android:verticalSpacing="10dp" >
    </GridView>

</LinearLayout>

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2、GridView中每个Item的布局文件grid_item_view.xml

<?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="100dp"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/application_icon"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:contentDescription="@string/app_name"
        android:src="@drawable/toggle" />

    <TextView
        android:id="@+id/application_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ellipsize="marquee"
        android:singleLine="true"
        android:textAppearance="?android:attr/textAppearanceSmall" />
    <!--
        android:focusable="true"
        android:focusableInTouchMode="true"


    -->

</LinearLayout>

注意：在代码中如果添加了上面注释的部分，则不会响应GridView 的onItemClick 方法。

3、WidgetGridViewActivity.java

package com.xy.zt.selfdefinewieget;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class WidgetGridViewActivity extends Activity {
    private GridView mAppGrid;
    private BaseAdapter mAdapter;
    PackageManager mPackManager;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.widget_gridview_layout);
        init();
    }

    private void init() {
        mAppGrid = (GridView) findViewById(R.id.show_app_grid_view);
        mPackManager = getPackageManager();
        List<ApplicationInfo> packInfo = mPackManager
                .getInstalledApplications(PackageManager.COMPONENT_ENABLED_STATE_ENABLED);

        mAdapter = new ApplicationAdapter(this, packInfo);
        mAppGrid.setAdapter(mAdapter);
        mAppGrid.setOnItemClickListener(new OnItemClickListener() {

            public void onItemClick(AdapterView<?> adaper, View v, int position, long id) {
                ApplicationInfo pInfo = (ApplicationInfo) mAdapter.getItem(position);
                Intent appIntent = mPackManager.getLaunchIntentForPackage(pInfo.packageName);
                if (appIntent == null) {
                    Toast.makeText(v.getContext(), "this is not a launcher activity !...",
                            Toast.LENGTH_SHORT).show();
                    return;
                }
                appIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                startActivity(appIntent);
            }

        });
    }

    private static class ApplicationAdapter extends BaseAdapter {
        private List<ApplicationInfo> mAppList;
        private LayoutInflater mInflater;
        private PackageManager mPackageManager;
        private Context mContext;

        public ApplicationAdapter(Context context, List<ApplicationInfo> appList) {
            if (context == null || appList == null)
                throw new IllegalArgumentException(
                        "exits null arguments  in constructor method of ApplicationAdapter ! ");
            mInflater = LayoutInflater.from(context);
            mAppList = new ArrayList<ApplicationInfo>();
            int len = appList.size();
            ApplicationInfo app;
            mPackageManager = context.getPackageManager();
            for (int i = 0; i < len; i++) {
                app = appList.get(i);
                if (mPackageManager.getLaunchIntentForPackage(app.packageName) == null) {
                    continue;
                }
                mAppList.add(app);
            }
            mContext = context;
        }

        public int getCount() {
            return mAppList.size();
        }

        public Object getItem(int position) {
            return mAppList.get(position);
        }

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

        public View getView(int position, View convertView, ViewGroup parent) {
            AppHolder holder;
            if (convertView == null) {
                convertView = mInflater.inflate(R.layout.grid_item_view, null);
                holder = new AppHolder();
                convertView.setTag(holder);
            } else {
                holder = (AppHolder) convertView.getTag();
            }
            holder.mAppIcon = (ImageView) convertView.findViewById(R.id.application_icon);
            holder.mAppName = (TextView) convertView.findViewById(R.id.application_name);
            initGridViewItem(mAppList.get(position), holder.mAppIcon, holder.mAppName);
            return convertView;
        }

        private void initGridViewItem(ApplicationInfo pInfo, ImageView img, TextView name) {
            String appName =
                    mPackageManager.getApplicationLabel(pInfo).toString();
            Drawable appIcon =
                    mPackageManager.getApplicationIcon(pInfo);
            img.setImageDrawable(appIcon);
            name.setText(appName);
//            final String packageName = pInfo.packageName;
            // name.setOnClickListener(new OnClickListener() {
            // public void onClick(View arg0) {
            // doLaunchApp(packageName);
            // }
            // });
            // img.setOnClickListener(new OnClickListener() {
            // public void onClick(View arg0) {
            // doLaunchApp(packageName);
            // }
            // });
        }

        // private void doLaunchApp(String packageName) {
        // Intent appIntent =
        // mPackageManager.getLaunchIntentForPackage(packageName);
        // Log.d("app_info", "start app from packageName : " + packageName);
        // mContext.startActivity(appIntent);
        // }

        private static class AppHolder {
            public ImageView mAppIcon;
            public TextView mAppName;
        }
    }
}

注意：上述代码中的注释部分的代码，添加后效果类似于XML文件中的android:focusable=”true” .

该部分代码主要使用到了PackageManager。PackManager.getInstalledApplications(PackageManager.COMPONENT_ENABLED_STATE_ENABLED);获取系统安装的应用程序信息。

在ApplicationAdapter的构造函数中有这么一段代码：

ApplicationInfo app;
            mPackageManager = context.getPackageManager();
            for (int i = 0; i < len; i++) {
                app = appList.get(i);
                if (mPackageManager.getLaunchIntentForPackage(app.packageName) == null) {
                    continue;
                }
                mAppList.add(app);
            }

它对初始的List做了一个简单的过滤，使得所有的图标点击后都能够进入响应的app。

下面代码加载应用的名称和图标信息：

String appName =
       mPackageManager.getApplicationLabel(pInfo).toString();
Drawable appIcon =
       mPackageManager.getApplicationIcon(pInfo);

在代码

ApplicationInfo pInfo = (ApplicationInfo) mAdapter.getItem(position);
                Intent appIntent = mPackManager.getLaunchIntentForPackage(pInfo.packageName);
                if (appIntent == null) {
                    Toast.makeText(v.getContext(), "this is not a launcher activity !...",
                            Toast.LENGTH_SHORT).show();
                    return;
                }
                appIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                startActivity(appIntent);

中通过packageManager获取category为Launcher 的Activity的intent。如果intent == null ，给出一个提示（系统中有些应用是没有入口activity的）。

4、在ViewData.java中添加如下内容（此部分内容可选，如有不清楚的地方参见一步一步学android控件（之一） —— 开始篇）

public static final int GRID_ID = EXPANDABLE_LIST_VIEW_ID + 1;
    public static final String GRID_NAME = "GridView";
private static final ViewData mGridView = new ViewData(GRID_NAME,
            GRID_ID);
View_Datas.add(mGridView);

WidgetsAdapter的handleItemClicked中添加如下内容：

case ViewData.GRID_ID:
                intent.setClass(mContext, WidgetGridViewActivity.class);
                mContext.startActivity(intent);
                break;

以上就是GridView的全部内容，下一个控件progressBar。

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