让自己的Android应用支持appwidget

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Android

经常看到一些教程教你如何写appwidget，但是，你知道你的appwidget是如何被添加到桌面上的吗？
          一般的，如果是做桌面的童鞋，基本上都会让自己的桌面支持appwidget。下面说说如何实现。
          首先是得定义一个承载appwidget的容器，系统的Launcher里面是用的CellLayout，实现的很不错。我这里就用一个简单的自定义ViewGroup来搞定，它是以长按的坐标处为要添加的appwidget的起始位置，简单点说就是按到哪儿就添加到哪儿.
1.package chroya.demo.widget;
2.
3.import android.content.Context;
4.import android.view.MotionEvent;
5.import android.view.View;
6.import android.view.ViewGroup;
7.
8./**
9. * 承载widget的容器
10. * @author chroya
11. */
12.public   class WidgetLayout extends ViewGroup {
13.    //存放touch的坐标
14.    private   int [] cellInfo = new   int [ 2 ];
15.    private OnLongClickListener mLongClickListener;
16.
17.    public WidgetLayout(Context context) {
18.        super (context);
19.        mLongClickListener = new OnLongClickListener() {
20.
21.            @Override
22.            public   boolean onLongClick(View v) {
23.
24.                return   false ;
25.            }
26.        };
27.    }
28.
29.    public   void addInScreen(View child, int width, int height) {
30.        LayoutParams lp = new LayoutParams(width, height);
31.        lp.x = cellInfo[0 ];
32.        lp.y = cellInfo[1 ];
33.        child.setOnLongClickListener(mLongClickListener);
34.        addView(child, lp);
35.    }
36.
37.    @Override
38.    protected   void onMeasure( int widthMeasureSpec, int heightMeasureSpec) {
39.        super .onMeasure(widthMeasureSpec, heightMeasureSpec);
40.        LayoutParams lp;
41.        for ( int index= 0 ; index<getChildCount(); index++) {
42.            lp = (LayoutParams) getChildAt(index).getLayoutParams();
43.            getChildAt(index).measure(
44.                    MeasureSpec.makeMeasureSpec(MeasureSpec.EXACTLY, lp.width),
45.                    MeasureSpec.makeMeasureSpec(MeasureSpec.EXACTLY, lp.height));
46.        }
47.    }
48.
49.    @Override
50.    public   boolean dispatchTouchEvent(MotionEvent event) {
51.        cellInfo[0 ] = ( int )event.getX();
52.        cellInfo[1 ] = ( int )event.getY();
53.        return   super .dispatchTouchEvent(event);
54.    }
55.
56.    @Override
57.    protected   void onLayout( boolean changed, int l, int t, int r, int b) {
58.        LayoutParams lp;
59.        for ( int index= 0 ; index<getChildCount(); index++) {
60.            lp = (LayoutParams) getChildAt(index).getLayoutParams();
61.            getChildAt(index).layout(lp.x, lp.y, lp.x+lp.width, lp.y+lp.height);
62.        }
63.    }
64.
65.    public   static   class LayoutParams extends ViewGroup.LayoutParams {
66.        int x;
67.        int y;
68.
69.        public LayoutParams( int width, int height) {
70.            super (width, height);
71.        }
72.    }
73.}

然后是重点了。还记得系统默认的桌面上，长按的时候出现的上下文菜单吗？里面有好几个选项，选择widget之后，会弹出一个已经安装的widget列表，选择一个widget之后，就会添加到桌面。我们可以把第一步去掉，长按之后，直接弹出已安装的widget列表，这是一个activity，用AppWidgetManager.ACTION_APPWIDGET_PICK这个Intent来启动，必须带上Extras，下面给出代码中有，不详叙。

1.package chroya.demo.widget;
2.
3.import   static android.util.Log.d;
4.
5.import java.util.ArrayList;
6.
7.import android.app.Activity;
8.import android.appwidget.AppWidgetHost;
9.import android.appwidget.AppWidgetManager;
10.import android.appwidget.AppWidgetProviderInfo;
11.import android.content.ComponentName;
12.import android.content.Intent;
13.import android.os.Bundle;
14.import android.view.View;
15.import android.view.View.OnLongClickListener;
16.
17./**
18. * 添加appwidget
19. * @author chroya
20. *
21. */
22.public   class Main extends Activity {
23.    private AppWidgetHost mAppWidgetHost;
24.    private AppWidgetManager mAppWidgetManager;
25.    private WidgetLayout layout;
26.
27.    private   static   final   int REQUEST_PICK_APPWIDGET = 1 ;
28.    private   static   final   int REQUEST_CREATE_APPWIDGET = 2 ;
29.    private   static   final   int APPWIDGET_HOST_ID = 0x100 ;
30.    private   static   final String EXTRA_CUSTOM_WIDGET = "custom_widget" ;
31.
32.    @Override
33.    public   void onCreate(Bundle savedInstanceState) {
34.        super .onCreate(savedInstanceState);
35.
36.        mAppWidgetManager = AppWidgetManager.getInstance(getApplicationContext());
37.        mAppWidgetHost = new AppWidgetHost(getApplicationContext(), APPWIDGET_HOST_ID);
38.        //开始监听widget的变化
39.        mAppWidgetHost.startListening();
40.
41.        layout = new WidgetLayout( this );
42.        layout.setOnLongClickListener(new OnLongClickListener() {
43.
44.            @Override
45.            public   boolean onLongClick(View v) {
46.
47.                addWidget();
48.                return   false ;
49.            }
50.        });
51.        setContentView(layout);
52.    }
53.
54.    @Override
55.    protected   void onActivityResult( int requestCode, int resultCode, Intent data) {
56.        if (resultCode == RESULT_OK) {
57.            switch (requestCode) {
58.            case REQUEST_PICK_APPWIDGET:
59.                addAppWidget(data);
60.                break ;
61.            case REQUEST_CREATE_APPWIDGET:
62.                completeAddAppWidget(data);
63.                break ;
64.            }
65.        } else   if (requestCode == REQUEST_PICK_APPWIDGET &&
66.                resultCode == RESULT_CANCELED && data != null ) {
67.            // Clean up the appWidgetId if we canceled
68.            int appWidgetId = data.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, - 1 );
69.            if (appWidgetId != - 1 ) {
70.                mAppWidgetHost.deleteAppWidgetId(appWidgetId);
71.            }
72.        }
73.    }
74.
75.    /**
76.     * 选中了某个widget之后，根据是否有配置来决定直接添加还是弹出配置activity
77.     * @param data
78.     */
79.    private   void addAppWidget(Intent data) {
80.        int appWidgetId = data.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, - 1 );
81.
82.        String customWidget = data.getStringExtra(EXTRA_CUSTOM_WIDGET);
83.        d("addAppWidget" , "data:" + customWidget);
84.        if ( "search_widget" .equals(customWidget)) {
85.            //这里直接将search_widget删掉了
86.            mAppWidgetHost.deleteAppWidgetId(appWidgetId);
87.        } else {
88.            AppWidgetProviderInfo appWidget = mAppWidgetManager.getAppWidgetInfo(appWidgetId);
89.
90.            d("addAppWidget" , "configure:" + appWidget.configure);
91.            if (appWidget.configure != null ) {
92.                //有配置，弹出配置
93.                Intent intent = new Intent(AppWidgetManager.ACTION_APPWIDGET_CONFIGURE);
94.                intent.setComponent(appWidget.configure);
95.                intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);
96.
97.                startActivityForResult(intent, REQUEST_CREATE_APPWIDGET);
98.            } else {
99.                //没有配置，直接添加
100.                onActivityResult(REQUEST_CREATE_APPWIDGET, Activity.RESULT_OK, data);
101.            }
102.        }
103.    }
104.
105.    /**
106.     * 请求添加一个新的widget
107.     */
108.    private   void addWidget() {
109.        int appWidgetId = mAppWidgetHost.allocateAppWidgetId();
110.
111.        Intent pickIntent = new Intent(AppWidgetManager.ACTION_APPWIDGET_PICK);
112.        pickIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);
113.        // add the search widget
114.        ArrayList<AppWidgetProviderInfo> customInfo =
115.                new ArrayList<AppWidgetProviderInfo>();
116.        AppWidgetProviderInfo info = new AppWidgetProviderInfo();
117.        info.provider = new ComponentName(getPackageName(), "XXX.YYY" );
118.        info.label = "Search" ;
119.        info.icon = R.drawable.ic_search_widget;
120.        customInfo.add(info);
121.        pickIntent.putParcelableArrayListExtra(
122.                AppWidgetManager.EXTRA_CUSTOM_INFO, customInfo);
123.        ArrayList<Bundle> customExtras = new ArrayList<Bundle>();
124.        Bundle b = new Bundle();
125.        b.putString(EXTRA_CUSTOM_WIDGET, "search_widget" );
126.        customExtras.add(b);
127.        pickIntent.putParcelableArrayListExtra(
128.                AppWidgetManager.EXTRA_CUSTOM_EXTRAS, customExtras);
129.        // start the pick activity
130.        startActivityForResult(pickIntent, REQUEST_PICK_APPWIDGET);
131.    }
132.
133.    /**
134.     * 添加widget
135.     * @param data
136.     */
137.    private   void completeAddAppWidget(Intent data) {
138.        Bundle extras = data.getExtras();
139.        int appWidgetId = extras.getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, - 1 );
140.
141.        d("completeAddAppWidget" , "dumping extras content=" +extras.toString());
142.        d("completeAddAppWidget" , "appWidgetId:" + appWidgetId);
143.        AppWidgetProviderInfo appWidgetInfo = mAppWidgetManager.getAppWidgetInfo(appWidgetId);
144.
145.        View hostView = mAppWidgetHost.createView(this , appWidgetId, appWidgetInfo);
146.
147.        layout.addInScreen(hostView, appWidgetInfo.minWidth, appWidgetInfo.minHeight);
148.    }
149.}

需要注意的几点：
1。必须调用AppWidgetHost的startListening方法来监听appwidget的状态变化，否则添加上去的appwidget不会更新的。
2。需要override一个onActivityResult方法，来接收添加appwidget和appwidget的配置activity的返回值。
3。启动AppWidgetManager.ACTION_APPWIDGET_PICK这个Intent，必须要给列表中加上自己定义的一个选项，否则出错。如本例中是用的Search。

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