Android:将View的内容映射成Bitmap

最近在做一个类似于游标的东西，由一个类似于seekbar的view来控制下端view内容的显示位置。所以需要将view中的内容映射成一张图片，设为seekbar的背景。所以就做了一些尝试，不过还有一些遗漏的小问题。

在Android中自有获取view中的cache内容，然后将内容转换成bitmap，方法名是：getDrawingCache(),返回结果为Bitmap，但是刚开始使用的时候，得到的结果都是null，所以在一个论坛里查到了正确的使用方法.代码如下：

Java代码
contentLayout.setDrawingCacheEnabled(true);
        contentLayout.measure(
                MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
                MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
        contentLayout.layout(0, 0, contentLayout.getMeasuredWidth(),
                contentLayout.getMeasuredHeight());

        contentLayout.buildDrawingCache();

        Bitmap bitmap= contentLayout.getDrawingCache();

contentLayout.setDrawingCacheEnabled(true);
  contentLayout.measure(
    MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
    MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
  contentLayout.layout(0, 0, contentLayout.getMeasuredWidth(),
    contentLayout.getMeasuredHeight());

  contentLayout.buildDrawingCache();

  Bitmap bitmap= contentLayout.getDrawingCache();
      最后就可以调用：Bitmap bitmap = view.getDrawingCache();就可以得到图片了。

为了测试这个功能，我使用了两种方式来创建LinerLayout中的内容，一种是在xml文件中就将view的内容添加了，只需在代码中添加对应ImageView中的图片就行了；另一种是动态添加LinerLayout中的View。

项目的主界面为：

接下来是SET_VIEW的代码:

Java代码
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.set_view);
    contentLayout = (LinearLayout) findViewById(R.id.content);
    imgSource1 = (ImageView) findViewById(R.id.imgSource1);
    imgSource2 = (ImageView) findViewById(R.id.imgSource2);
    imgCache = (ImageView) findViewById(R.id.imgCache);

    imgSource1.setImageResource(R.drawable.source1);
    imgSource2.setImageResource(R.drawable.source2);

    contentLayout.setDrawingCacheEnabled(true);
    contentLayout.measure(
            MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
            MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
    contentLayout.layout(0, 0, contentLayout.getMeasuredWidth(),
            contentLayout.getMeasuredHeight());

    contentLayout.buildDrawingCache();

    Bitmap bitmap= contentLayout.getDrawingCache();
    if(bitmap!=null){
        imgCache.setImageBitmap(bitmap);
    }else{
        Log.i("CACHE_BITMAP", "DrawingCache=null");
    }
}

public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.set_view);
  contentLayout = (LinearLayout) findViewById(R.id.content);
  imgSource1 = (ImageView) findViewById(R.id.imgSource1);
  imgSource2 = (ImageView) findViewById(R.id.imgSource2);
  imgCache = (ImageView) findViewById(R.id.imgCache);

  imgSource1.setImageResource(R.drawable.source1);
  imgSource2.setImageResource(R.drawable.source2);

  contentLayout.setDrawingCacheEnabled(true);
  contentLayout.measure(
    MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
    MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
  contentLayout.layout(0, 0, contentLayout.getMeasuredWidth(),
    contentLayout.getMeasuredHeight());

  contentLayout.buildDrawingCache();

  Bitmap bitmap= contentLayout.getDrawingCache();
  if(bitmap!=null){
   imgCache.setImageBitmap(bitmap);
  }else{
   Log.i("CACHE_BITMAP", "DrawingCache=null");
  }
}

set_view.xml布局文件为：

Xml代码
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <TextView android:text="set_view" android:layout_width="fill_parent"
        android:layout_height="wrap_content"></TextView>
    <LinearLayout android:id="@+id/content"
        android:orientation="vertical" android:layout_width="wrap_content"
        android:layout_height="wrap_content">
        <ImageView android:id="@+id/imgSource1"
            android:layout_width="wrap_content" android:layout_height="wrap_content"></ImageView>
        <ImageView android:id="@+id/imgSource2"
            android:layout_width="wrap_content" android:layout_height="wrap_content"></ImageView>
    </LinearLayout>

    <LinearLayout android:id="@+id/cache"
        android:layout_width="wrap_content" android:layout_height="wrap_content">

补充：移动开发 , Android ,