让自己的Android应用支持appwidget

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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。
Java代码
package chroya.demo.widget;

import android.content.Context;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;

/**
* 承载widget的容器
* @author chroya
*/
public class WidgetLayout extends ViewGroup {
    //存放touch的坐标
    private int[] cellInfo = new int[2];
    private OnLongClickListener mLongClickListener;

    public WidgetLayout(Context context) {
        super(context);
        mLongClickListener = new OnLongClickListener() {

            @Override
            public boolean onLongClick(View v) {

                return false;
            }
        };
    }

    public void addInScreen(View child, int width, int height) {
        LayoutParams lp = new LayoutParams(width, height);
        lp.x = cellInfo[0];
        lp.y = cellInfo[1];
        child.setOnLongClickListener(mLongClickListener);
        addView(child, lp);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        LayoutParams lp;
        for(int index=0; index<getChildCount(); index++) {
            lp = (LayoutParams) getChildAt(index).getLayoutParams();
            getChildAt(index).measure(
                    MeasureSpec.makeMeasureSpec(MeasureSpec.EXACTLY, lp.width),
                    MeasureSpec.makeMeasureSpec(MeasureSpec.EXACTLY, lp.height));
        }
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        cellInfo[0] = (int)event.getX();
        cellInfo[1] = (int)event.getY();
        return super.dispatchTouchEvent(event);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        LayoutParams lp;
        for(int index=0; index<getChildCount(); index++) {
            lp = (LayoutParams) getChildAt(index).getLayoutParams();
            getChildAt(index).layout(lp.x, lp.y, lp.x+lp.width, lp.y+lp.height);
        }
    }

    public static class LayoutParams extends ViewGroup.LayoutParams {
        int x;
        int y;

        public LayoutParams(int width, int height) {
            super(width, height);
        }
    }
}

        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。
Java代码
package chroya.demo.widget;

import static android.util.Log.d;

import java.util.ArrayList;

import android.app.Activity;
import android.appwidget.AppWidgetHost;
import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProviderInfo;
import android.content.ComponentName;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnLongClickListener;

/**
* 添加appwidget
* @author chroya
*
*/
public class Main extends Activity {
    private AppWidgetHost mAppWidgetHost;
    private AppWidgetManager mAppWidgetManager;
    private WidgetLayout layout;

    private static final int REQUEST_PICK_APPWIDGET = 1;
    private static final int REQUEST_CREATE_APPWIDGET = 2;
    private static final int APPWIDGET_HOST_ID = 0x100;
    private static final String EXTRA_CUSTOM_WIDGET = "custom_widget";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mAppWidgetManager = AppWidgetManager.getInstance(getApplicationContext());
        mAppWidgetHost = new AppWidgetHost(getApplicationContext(), APPWIDGET_HOST_ID);
        //开始监听widget的变化
        mAppWidgetHost.startListening();

        layout = new WidgetLayout(this);
        layout.setOnLongClickListener(new OnLongClickListener() {

            @Override
            public boolean onLongClick(View v) {

                addWidget();
                return false;
            }
        });
        setContentView(layout);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (resultCode == RESULT_OK) {
            switch (requestCode) {
            case REQUEST_PICK_APPWIDGET:
                addAppWidget(data);
                break;
            case REQUEST_CREATE_APPWIDGET:
                completeAddAppWidget(data);
                break;
            }
        } else if (requestCode == REQUEST_PICK_APPWIDGET &&
                resultCode == RESULT_CANCELED && data != null) {
            // Clean up the appWidgetId if we canceled
            int appWidgetId = data.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, -1);
            if (appWidgetId != -1) {
                mAppWidgetHost.deleteAppWidgetId(appWidgetId);
            }
        }
    }

    /**
     * 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
     * @param data
     */
    private void addAppWidget(Intent data) {
        int appWidgetId = data.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, -1);

        String customWidget = data.getStringExtra(EXTRA_CUSTOM_WIDGET);
        d("addAppWidget", "data:"+ customWidget);
        if ("search_widget".equals(customWidget)) {
            //这里直接将search_widget删掉了
            mAppWidgetHost.deleteAppWidgetId(appWidgetId);
        } else {
            AppWidgetProviderInfo appWidget = mAppWidgetManager.getAppWidgetInfo(appWidgetId);

            d("addAppWidget", "configure:"+ appWidget.configure);
            if (appWidget.configure != null) {
                //有配置，弹出配置
                Intent intent = new Intent(AppWidgetManager.ACTION_APPWIDGET_CONFIGURE);
                intent.setComponent(appWidget.configure);
                intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);

                startActivityForResult(intent, REQUEST_CREATE_APPWIDGET);
            } else {
                //没有配置，直接添加
                onActivityResult(REQUEST_CREATE_APPWIDGET, Activity.RESULT_OK, data);
            }
        }
    }

    /**
     * 请求添加一个新的widget
     */
    private void addWidget() {
        int appWidgetId = mAppWidgetHost.allocateAppWidgetId();

        Intent pickIntent = new Intent(AppWidgetManager.ACTION_APPWIDGET_PICK);
        pickIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);
        // add the search widget
        ArrayList<AppWidgetProviderInfo> customInfo =
                new ArrayList<AppWidgetProviderInfo>();
        AppWidgetProviderInfo info = new AppWidgetProviderInfo();
        info.provider = new ComponentName(getPackageName(), "XXX.YYY");
        info.label = "Search";
        info.icon = R.drawable.ic_search_widget;
        customInfo.add(info);
        pickIntent.putParcelableArrayListExtra(
                AppWidgetManager.EXTRA_CUSTOM_INFO, customInfo);
        ArrayList<Bundle> customExtras = new ArrayList<Bundle>();
        Bundle b = new Bundle();
        b.putString(EXTRA_CUSTOM_WIDGET, "search_widget");
        customExtras.add(b);
        pickIntent.putParcelableArrayListExtra(
                AppWidgetManager.EXTRA_CUSTOM_EXTRAS, customExtras);
        // start the pick activity
        startActivityForResult(pickIntent, REQUEST_PICK_APPWIDGET);
    }

    /**
     * 添加widget
     * @param data
     */
    private void completeAddAppWidget(Intent data) {
        Bundle extras = data.getExtras();
        int appWidgetId = extras.getInt(AppWidgetManager.EXTRA_APPWIDGET_ID, -1);

        d("completeAddAppWidget", "dumping extras content="+extras.toString());
        d("completeAddAppWidget", "appWidgetId:"+ appWidgetId);
        AppWidgetProviderInfo appWidgetInfo = mAppWidgetManager.getAppWidgetInfo(appWidgetId);

        View hostView = mAppWidgetHost.createView(this, appWidgetId, appWidgetInfo);

        layout.addInScreen(hostView, appWidgetInfo.minWidth, appWidgetInfo.minHeight);
    }
}