我正在尝试创建一个自定义视图,用户可以在其中绘制其签名.您可以在其中以编程方式将其放置到视图中并设置大小等.我之前没有做过此操作,因此我将其基于android api演示的fingerpaint类.现在的问题是,它会在方向改变时擦除对象,我不确定如何使它不这样做.
PaintView的代码
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
private boolean mDrawPoint;
private int stateToSave;
private Paint mPaint;
public PaintView(Context context) {
super(context);
System.out.println("init");
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
setupPaint();
}
private void setupPaint()
{
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(0xFF000000);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(4);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
System.out.println("w "+w+" h "+h+" oldw "+oldw+" oldh "+oldh);
mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
}
@Override
protected void onDraw(Canvas canvas) {
System.out.println("on draw");
canvas.drawColor(0xFFAAAAAA);
canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
canvas.drawPath(mPath, mPaint);
}
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
private void touch_start(float x, float y) {
mPath.reset();
mPath.moveTo(x, y);
mX = x;
mY = y;
mDrawPoint=true;
}
private void touch_move(float x, float y) {
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
mDrawPoint=false;
mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
mX = x;
mY = y;
}
}
private void touch_up() {
if(mDrawPoint == true) {
mCanvas.drawPoint(mX, mY, mPaint);
} else {
mPath.lineTo(mX, mY);
// commit the path to our offscreen
mCanvas.drawPath(mPath, mPaint);
// kill this so we don't double draw
mPath.reset();
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
getParent().requestDisallowInterceptTouchEvent(true);
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
}
作为一项迷你测试,我加入了
@Override
public Parcelable onSaveInstanceState()
{
System.out.println("save instance");
stateToSave++;
Bundle bundle = new Bundle();
bundle.putParcelable("instanceState", super.onSaveInstanceState());
bundle.putInt("stateToSave", this.stateToSave);
return bundle;
}
@Override
public void onRestoreInstanceState(Parcelable state)
{
System.out.println("on restore");
if (state instanceof Bundle)
{
System.out.println("on restore");
Bundle bundle = (Bundle) state;
this.stateToSave = bundle.getInt("stateToSave");
super.onRestoreInstanceState(bundle.getParcelable("instanceState"));
System.out.println(stateToSave);
return;
}
super.onRestoreInstanceState(state);
}
但是onRestoreInstance()和onSaveInstance()永远不会在方向更改时被调用.这是我进行paintview活动的oncreate中的代码.
RelativeLayout inner= (RelativeLayout) findViewById(R.id.inner);
int width=600;
int height=360;
float X= 100;
float Y=60;
LayoutParams wrapped = new LayoutParams(width,height);
PaintView painting=new PaintView(this);
painting.setX(X);
painting.setY(Y);
painting.setLayoutParams(wrapped);
inner.addView(painting);
编辑：我想出了为什么saveinstancestate没有调用,我必须给View提供一个ID,然后它才能工作.
painting.setId(4);
现在,我需要弄清楚如何使其保存图形.
解决方法:
您需要确保您的视图为saveEnabled,请尝试：
setSaveEnabled(true);
您可以从PaintView的构造函数中执行此操作.
另外,您可能需要确保在方向改变时您的活动被销毁/重新创建.确保您没有：
<activity name="?"
android:configChanges="keyboardHidden|orientation"
/>
使用此View为该活动声明的活动,否则该活动不会在方向更改时被破坏.另外,如果您在这些活动中覆盖了onSaveInstanceState / * onRestoreInstanceState *,则需要调用相应的超类方法,即super.onSaveInstanceState()或super.onRestoreInstanceState()).
至于如何实际重新创建或保存图像以改变方向,如何保存以某种可打包列表完成的每个事件的方式.将该列表保存在onSaveInstanceState中,然后将其还原到onRestoreInstanceState中.然后获取事件列表并遍历事件列表,调用相应的绘制函数.
您可能需要根据新方向对X,Y值进行一些转换.
代码看起来像这样：
public class PaintView extends View {
private static final String EXTRA_EVENT_LIST = "event_list";
private static final String EXTRA_STATE = "instance_state";
private ArrayList<MotionEvent> eventList = new ArrayList<MotionEvent>(100);
@Override
public boolean onTouchEvent(MotionEvent event) {
getParent().requestDisallowInterceptTouchEvent(true);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
case MotionEvent.ACTION_UP:
performTouchEvent(event);
}
return true;
}
private void performTouchEvent(MotionEvent event) {
float x = event.getX();
float y = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
break;
case MotionEvent.ACTION_UP:
touch_up();
break;
}
invalidate();
eventList.add(MotionEvent.obtain(event));
}
}
@Override
public Parcelable onSaveInstanceState()
{
System.out.println("save instance");
Bundle bundle = new Bundle();
bundle.putParcelable(EXTRA_STATE, super.onSaveInstanceState());
bundle.putParcelableArrayList(EXTRA_EVENT_LIST, eventList);
return bundle;
}
@Override
public void onRestoreInstanceState(Parcelable state)
{
if (state instanceof Bundle)
{
Bundle bundle = (Bundle) state;
super.onRestoreInstanceState(bundle.getParcelable(EXTRA_STATE));
eventList = bundle.getParcelableArrayList(EXTRA_EVENT_LIST);
if (eventList == null) {
eventList = new ArrayList<MotionEvent>(100);
}
for (MotionEvent event : eventList) {
performTouchEvent(event);
}
return;
}
super.onRestoreInstanceState(state);
}
}