在Android应用中，作者遇到一个问题：当在ScrollView内的TextView滚动时，尝试将TextView的内容绘制到Bitmap，但Bitmap始终只显示TextView的初始内容，而非当前可见的部分。作者尝试了不同的解决方案，包括在触摸事件中更新Bitmap和在自定义TextView中覆盖onDraw方法，但问题仍未解决。博客中提供了相关的代码示例以展示问题所在。
我在ScrollView中有一个TextView：
TextView有很多文本,这就是可滚动的原因.我需要在TextView中将当前可见内容绘制到Bitmap.出于测试目的,我在ImageView中显示此位图.我有以下代码：
public class TextviewToImageActivity extends Activity {
private TextView textView;
private ScrollView textAreaScroller;
private ImageView imageView;
private Handler mHandler;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mHandler = new Handler();
imageView = (ImageView) findViewById(R.id.imageView);
textAreaScroller = (ScrollView) findViewById(R.id.textAreaScroller);
textView = (TextView) findViewById(R.id.scrapbook);
textView.setOnTouchListener(new OnTouchListener() {
public boolean onTouch(View v,MotionEvent event) {
imageView.setImageBitmap(loadBitmapFromView(textAreaScroller));
return false;
}
});
Button upBtn = (Button) findViewById(R.id.upBtn);
Button downBtn = (Button) findViewById(R.id.downBtn);
upBtn.setOnTouchListener(new OnTouchListener() {
public boolean onTouch(View v,MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
scheduleScroller(upScroller);
imageView.setImageBitmap(loadBitmapFromView(textView));
} else if (event.getAction() == MotionEvent.ACTION_UP) {
mHandler.removeMessages(1);
}
return true;
}
});
downBtn.setOnTouchListener(new OnTouchListener() {
public boolean onTouch(View v,MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
scheduleScroller(downScroller);
imageView.setImageBitmap(loadBitmapFromView(textView));
} else if (event.getAction() == MotionEvent.ACTION_UP) {
mHandler.removeMessages(1);
}
return true;
}
});
loadDoc();
}
private Runnable downScroller = new Runnable() {
public void run() {
textAreaScroller.scrollBy(0,10);
scheduleScroller(downScroller);
}
};
private Runnable upScroller = new Runnable() {
public void run() {
textAreaScroller.scrollBy(0,-10);
scheduleScroller(upScroller);
}
};
private void scheduleScroller(Runnable scrollerJob) {
Message msg = Message.obtain(mHandler,scrollerJob);
msg.what = 1;
mHandler.sendMessageDelayed(msg,10);
}
private static Bitmap loadBitmapFromView(View v) {
Bitmap b = Bitmap.createBitmap(400,200,Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(b);
v.draw(c);
return b;
}
private void loadDoc() {
String s = "";
for (int x = 0; x <= 100; x++) {
s += "Line: " + String.valueOf(x) + "\n";
}
textView.setText(s);
textView.setMovementMethod(new ScrollingMovementMethod());
}
}
问题是,一旦我滚动TextView(触发TouchEvent),Bitmap不会反映TextView的当前内容,而是始终只有TextView的开头内容(当前滚动位置无关紧要).我更新了帖子以提供工作代码 – 也许它可以在sb的其他设备上运行.
UPDATE
我还尝试通过在我的自定义TextView中覆盖onDraw来检查WarrenFaith的想法,但它仍然只是绘制TextView的开头内容：
public class MyTextView extends TextView {
private Bitmap mBitmap;
public MyTextView(Context context,AttributeSet attrs) {
super(context,attrs);
}
public MyTextView(Context context) {
super(context);
}
public MyTextView(Context context,AttributeSet attrs,int defStyle) {
super(context,attrs,defStyle);
}
public Bitmap getBitmap() {
return mBitmap;
}
@Override
protected void onDraw(Canvas canvas) {
mBitmap = Bitmap.createBitmap(canvas.getWidth(),canvas.getHeight(),Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(mBitmap);
super.onDraw(canvas);
super.onDraw(c);
}
}
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