blocks|key|1318679|text|我也遇到了这个问题，我找到了这个答案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1318680|v.setDrawingCacheEnabled(true);

//+this+is+the+important+code+:)++
//+Without+it+the+view+will+have+a+dimension+of+0,0+and+the+bitmap+will+be+null++++++++++
v.measure(MeasureSpec.makeMeasureSpec(0,+MeasureSpec.UNSPECIFIED),+
++++++++++++MeasureSpec.makeMeasureSpec(0,+MeasureSpec.UNSPECIFIED));
v.layout(0,+0,+v.getMeasuredWidth(),+v.getMeasuredHeight());+

v.buildDrawingCache(true);
Bitmap+b+=+Bitmap.createBitmap(v.getDrawingCache());
v.setDrawingCacheEnabled(false);+//+clear+drawing+cache|code-block|syntax|javascript|1318681|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I was having this problem also and found this answer:

<pre><code>v.setDrawingCacheEnabled(true);

// this is the important code :) 
// Without it the view will have a dimension of 0,0 and the bitmap will be null 
v.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), 
 MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
v.layout(0, 0, v.getMeasuredWidth(), v.getMeasuredHeight()); 

v.buildDrawingCache(true);
Bitmap b = Bitmap.createBitmap(v.getDrawingCache());
v.setDrawingCacheEnabled(false); // clear drawing cache
</code></pre>

blocks|key|1103778|text|如果getDrawingCache总是returning+null+guys:使用这个：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1103779|public+static+Bitmap+loadBitmapFromView(View+v)+{
+++++Bitmap+b+=+Bitmap.createBitmap(+v.getLayoutParams().width,+v.getLayoutParams().height,+Bitmap.Config.ARGB_8888);++++++++++++++++
+++++Canvas+c+=+new+Canvas(b);
+++++v.layout(0,+0,+v.getLayoutParams().width,+v.getLayoutParams().height);
+++++v.draw(c);
+++++return+b;
}|code-block|syntax|javascript|1103780|参考：https://stackoverflow.com/a/6272951/371749|1103781|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/6272951/371749^0|2|F|J|E|0|0|3|16|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|D|@$9|11|A|12|1|13]]|E|$]]|$1|M|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

if <code>getDrawingCache</code> is always <code>returning null</code> guys:
use this:

<pre><code>public static Bitmap loadBitmapFromView(View v) {
 Bitmap b = Bitmap.createBitmap( v.getLayoutParams().width, v.getLayoutParams().height, Bitmap.Config.ARGB_8888); 
 Canvas c = new Canvas(b);
 v.layout(0, 0, v.getLayoutParams().width, v.getLayoutParams().height);
 v.draw(c);
 return b;
}
</code></pre>

Reference: <a href="https://stackoverflow.com/a/6272951/371749">https://stackoverflow.com/a/6272951/371749</a>

blocks|key|1318792|text|如果你想捕捉的视图真的显示在屏幕上，但它返回null。这意味着您可以在窗口管理器生成视图之前捕获它。有些布局非常复杂。如果layout包含嵌套布局layout_weight..etc，它会导致多次重新布局以获得准确的大小。最好的解决方案是等待窗口管理器完成工作，然后获取屏幕截图。尝试将getDrawingCache()放入处理程序中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1318793|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If the view you want catch really shows on screen, but it return null. That means you catch the view before Window manager generate it. Some layouts are very complicated. If layout includes nested layouts, layout_weight..etc, it causes several times relayout to get exactly size. The best solution is waiting until window manager finish job and then get screen shot. Try to put getDrawingCache() in handler.

blocks|key|1103876|text|我用的是这个。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1103877|myView.getViewTreeObserver().addOnGlobalLayoutListener(new+ViewTreeObserver.OnGlobalLayoutListener()+{
++++++++@Override
++++++++public+void+onGlobalLayout()+{
++++++++++++Bitmap+bitmap+=+Bitmap.createBitmap(myView.getDrawingCache());
++++++++}
++++});|code-block|syntax|javascript|1103878|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Im using this instead.

<pre><code>myView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
 @Override
 public void onGlobalLayout() {
 Bitmap bitmap = Bitmap.createBitmap(myView.getDrawingCache());
 }
 });
</code></pre>

blocks|key|1318912|text|获取空值的基本原因是视图没有被忽略。那么，所有使用view.getWidth()、view.getLayoutParams()、.width等的尝试，包括view.getDrawingCache()和view.buildDrawingCache()，都是无用的。因此，首先需要设置视图的尺寸，例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1318913|view.layout(0,+0,+width,+height);|code-block|syntax|javascript|1318914|(您已经根据自己的喜好设置了“width”和“height”，或者使用WindowManager等工具获取了它们。)|1318915|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

The basic reason one gets nulls is that the view is not dimentioned. All attempts then, using view.getWidth(), view.getLayoutParams().width, etc., including view.getDrawingCache() and view.buildDrawingCache(), are useless.
So, you need first to set dimensions to the view, e.g.:

<pre><code>view.layout(0, 0, width, height);
</code></pre>

(You have already set 'width' and 'height' as you like or obtained them with WindowManager, etc.)

blocks|key|1318991|text|我正在尝试基于视图动态创建n个图像。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1318992|LayoutInflater+infalter=(LayoutInflater)getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
final+View+addview=infalter.inflate(R.layout.barcode_image_list_row_item,+null);
final+ImageView+imv=(ImageView)+addview.findViewById(R.id.imageView1);
final+TextView+tv=(TextView)+addview.findViewById(R.id.textView1);

try+{+++++++++
++++final+Bitmap+bitmap+=+encodeAsBitmap(""%2Bvalue,+BarcodeFormat.CODE_128,+600,+300);

++++if+(bitmap+!=+null)+{
++++++++//+TODO+Auto-generated+method+stub
++++++++imv.setImageBitmap(bitmap);
++++++++tv.setText(value);

++++++++addview.setDrawingCacheEnabled(true);

++++++++//+this+is+the+important+code+:)++
++++++++//+Without+it+the+view+will+have+a+dimension+of+0,0+and+the+bitmap+will+be+null++++++++++
++++++++addview.measure(MeasureSpec.makeMeasureSpec(0,+MeasureSpec.UNSPECIFIED),+
++++++++++++++++++++++++MeasureSpec.makeMeasureSpec(0,+MeasureSpec.UNSPECIFIED));
++++++++addview.layout(0,+0,+addview.getMeasuredWidth(),+addview.getMeasuredHeight());+

++++++++addview.buildDrawingCache(true);
++++++++Bitmap+b+=+Bitmap.createBitmap(addview.getDrawingCache());
++++++++addview.setDrawingCacheEnabled(false);+//+clear+drawing+cache
++++++++//+saving+the+bitmap+++
++++++++savebarcode(b,value);
++++}
}+catch+(WriterException+e)+{
++++e.printStackTrace();
}|code-block|syntax|javascript|1318993|我认为这段代码会帮助某些人..|1318994|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I am trying to creating the n number of images dynamically based on view. 

<pre><code>LayoutInflater infalter=(LayoutInflater)getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
final View addview=infalter.inflate(R.layout.barcode_image_list_row_item, null);
final ImageView imv=(ImageView) addview.findViewById(R.id.imageView1);
final TextView tv=(TextView) addview.findViewById(R.id.textView1);

try { 
 final Bitmap bitmap = encodeAsBitmap(""+value, BarcodeFormat.CODE_128, 600, 300);

 if (bitmap != null) {
 // TODO Auto-generated method stub
 imv.setImageBitmap(bitmap);
 tv.setText(value);

 addview.setDrawingCacheEnabled(true);

 // this is the important code :) 
 // Without it the view will have a dimension of 0,0 and the bitmap will be null 
 addview.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), 
 MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
 addview.layout(0, 0, addview.getMeasuredWidth(), addview.getMeasuredHeight()); 

 addview.buildDrawingCache(true);
 Bitmap b = Bitmap.createBitmap(addview.getDrawingCache());
 addview.setDrawingCacheEnabled(false); // clear drawing cache
 // saving the bitmap 
 savebarcode(b,value);
 }
} catch (WriterException e) {
 e.printStackTrace();
}
</code></pre>

I think this code will help someone..

blocks|key|1104104|text|工作最好4me|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1104105|++++Bitmap+bitmap+=+Bitmap.createBitmap(+screen.getMeasuredWidth(),+screen.getMeasuredHeight(),+Bitmap.Config.ARGB_8888);
++++Canvas+canvas+=+new+Canvas(bitmap);
++++screen.layout(0,+0,+screen.getMeasuredWidth(),+screen.getMeasuredHeight());
++++screen.draw(canvas);|code-block|syntax|javascript|1104106|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Work best 4me

<pre><code> Bitmap bitmap = Bitmap.createBitmap( screen.getMeasuredWidth(), screen.getMeasuredHeight(), Bitmap.Config.ARGB_8888);
 Canvas canvas = new Canvas(bitmap);
 screen.layout(0, 0, screen.getMeasuredWidth(), screen.getMeasuredHeight());
 screen.draw(canvas);
</code></pre>

blocks|key|1319073|text|这是获取位图的简单而有效的方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1319074|public+void+addView(View+v)+{
++++++++v.setDrawingCacheEnabled(true);
++++++++v.buildDrawingCache();

++++++++Bitmap+bitmap+=+v.getDrawingCache();

++++++++if(bitmap+==+null)+{
++++++++++++//+bitmap+is+null
++++++++++++//+do+whatever+you+want
++++++++}+else+{
++++++++++++setImageBitmap(bitmap);
++++++++}
++++++++v.setDrawingCacheEnabled(false);
++++++++v.destroyDrawingCache();
++++}|code-block|syntax|javascript|1319075|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This the simple and efficient way to get bitmap

<pre><code>public void addView(View v) {
 v.setDrawingCacheEnabled(true);
 v.buildDrawingCache();

 Bitmap bitmap = v.getDrawingCache();

 if(bitmap == null) {
 // bitmap is null
 // do whatever you want
 } else {
 setImageBitmap(bitmap);
 }
 v.setDrawingCacheEnabled(false);
 v.destroyDrawingCache();
 }
</code></pre>

Would anyone please try to explain to me why

<pre><code>public void addView(View child) {
 child.setDrawingCacheEnabled(true);
 child.setWillNotCacheDrawing(false);
 child.setWillNotDraw(false);
 child.buildDrawingCache();
 if(child.getDrawingCache() == null) { //TODO Make this work!
 Log.w("View", "View child's drawing cache is null");
 }
 setImageBitmap(child.getDrawingCache()); //TODO MAKE THIS WORK!!!
}
</code></pre>

ALWAYS logs that the drawing cache is null, and sets the bitmap to null?

Do I have to actually draw the view before the cache is set?

Thanks!

Android View.getDrawingCache returns null, only null

有没有人能给我解释一下为什么public void addView(View child) {  child.setDrawingCacheEnabled(true);  child.setWillNotCacheDrawing(false);  child.setWillNotDraw(false);  child....

问Android View.getDrawingCache返回null，仅返回null
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