我在当前工作中的某个项目中遇到了一些非常棘手的问题，要么没有可用的好信息，要么好信息被埋藏在海量的坏信息下面。
我已经解决了这些问题，并计划与所有开发人员分享一个简单的示例，以获取手指的触摸和运动事件，并进行绘制**。
2个回答
13
按照以下步骤操作：
1) 创建一个视图类，继承View，并创建构造函数
覆盖 onDraw() 方法。你需要添加手指触碰和移动的路径。为此目的，你需要重写onTouch()方法。在你的onDraw()方法中，使用自己选择的画笔绘制路径。你应该调用invalidate()来刷新视图。
//drawing path
static Path drawPath;
//drawing and canvas paint
private Paint drawPaint, canvasPaint;
//initial color
static int paintColor = 0xFFFF0000;
//stroke width
private float STROKE_WIDTH = 5f;
//canvas
private Canvas drawCanvas;
//canvas bitmap
private Bitmap canvasBitmap;
//eraser mode
private boolean erase=false;
//constructor
public DrawingView(Context context, AttributeSet attrs){
super(context, attrs);
setupDrawing();
setErase(erase);
}
private void setupDrawing(){
drawPath = new Path();
drawPaint = new Paint();
drawPaint.setColor(paintColor);
drawPaint.setAntiAlias(true);
drawPaint.setStrokeWidth(STROKE_WIDTH);
drawPaint.setStyle(Paint.Style.STROKE);
drawPaint.setStrokeJoin(Paint.Join.ROUND);
drawPaint.setStrokeCap(Paint.Cap.ROUND);
canvasPaint = new Paint(Paint.DITHER_FLAG);
}
//*************************************** View assigned size ****************************************************
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
drawCanvas = new Canvas(canvasBitmap);
}
public void setErase(boolean isErase){
erase=isErase;
drawPaint = new Paint();
if(erase) {
setupDrawing();
int srcColor= 0x00000000;
PorterDuff.Mode mode = PorterDuff.Mode.CLEAR;
PorterDuffColorFilter porterDuffColorFilter = new PorterDuffColorFilter(srcColor, mode);
drawPaint.setColorFilter(porterDuffColorFilter);
drawPaint.setColor(srcColor);
drawPaint.setXfermode(new PorterDuffXfermode(mode));
}
else {
setupDrawing();
}
}
//************************************ draw view *************************************************************
@Override
protected void onDraw(Canvas canvas) {
canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
canvas.drawPath(drawPath, drawPaint);
}
//*************************** respond to touch interaction **************************************************
@Override
public boolean onTouchEvent(MotionEvent event) {
canvasPaint.setColor(paintColor);
float touchX = event.getX();
float touchY = event.getY();
//respond to down, move and up events
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
drawPath.moveTo(touchX, touchY);
break;
case MotionEvent.ACTION_MOVE:
drawCanvas.drawPath(drawPath, drawPaint);
drawPath.lineTo(touchX, touchY);
break;
case MotionEvent.ACTION_UP:
drawPath.lineTo(touchX, touchY);
drawCanvas.drawPath(drawPath, drawPaint);
drawPath.reset();
break;
default:
return false;
}
//redraw
invalidate();
return true;
}
//*********************************** return current alpha ***********************************************
public int getPaintAlpha(){
return Math.round((float)STROKE_WIDTH/255*100);
}
//************************************** set alpha ******************************************************
public void setPaintAlpha(int newAlpha){
STROKE_WIDTH=Math.round((float)newAlpha/100*255);
drawPaint.setStrokeWidth(newAlpha);
}
}
2) 你的活动：
SeekBar mThickness;
private DrawingView mDrawLayout;
Button erase, draw;
private Paint drawPaint = new Paint();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mThickness = (SeekBar) findViewById(R.id.thickness);
mDrawLayout = (DrawingView) findViewById(R.id.viewDraw);
erase = (Button) findViewById(R.id.erase);
draw= (Button) findViewById(R.id.draw);
mDrawLayout.setVisibility(View.VISIBLE);
mDrawLayout.setDrawingCacheEnabled(true);
mDrawLayout.setEnabled(true);
mThickness.setMax(50);
mThickness.setProgress(10);
mDrawLayout.setPaintAlpha(mThickness.getProgress());
int currLevel = mDrawLayout.getPaintAlpha();
mThickness.setProgress(currLevel);
mDrawLayout.invalidate();
erase.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
drawPaint.setColor(Color.TRANSPARENT);
mDrawLayout.setErase(true);
}
});
draw.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
mDrawLayout.setErase(false);
}
});
mThickness.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
mDrawLayout.setPaintAlpha(mThickness.getProgress());
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
3) XML：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
tools:context=".MainActivity" >
<com.example.drawdemo.DrawingView
android:id="@+id/viewDraw"
android:layout_width="wrap_content"
android:layout_height="200dp"
android:layout_marginTop="20dp"
android:scaleType="fitXY" />
<SeekBar
android:id="@+id/thickness"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/viewDraw"
android:layout_marginTop="25dp" />
<Button
android:id="@+id/erase"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/thickness"
android:text="erase" />
<Button
android:id="@+id/draw"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/erase"
android:text="draw" />
</RelativeLayout>
- Namrata
2
创建一个继承自View的类，将下面的代码粘贴到该类中。
在XML中，粘贴以下代码：
public class CustomClass extends View {
private Paint paint = new Paint();
private Path path = new Path();
public CustomClass(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
paint.setAntiAlias(true);
paint.setStrokeWidth(5 f);
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
}
@Override protected void onDraw(Canvas canvas) {
canvas.drawPath(path, paint);
}
@Override public boolean onTouchEvent(MotionEvent event) {
// Get the coordinates of the touch event.
float eventX = event.getX();
float eventY = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
// Set a new starting point
path.moveTo(eventX, eventY);
return true;
case MotionEvent.ACTION_MOVE:
// Connect the points
path.lineTo(eventX, eventY);
break;
default:
return false;
}
// Makes our view repaint and call onDraw
invalidate();
return true;
}
}
在XML中，粘贴以下代码：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffffff">
<!-- This is the view on which we will draw. -->
<view
android:layout_width="match_parent"
android:layout_height="200sp"
class="com.example.gopal.drawing.MainDrawingView"
android:id="@+id/custom_view"
android:layout_gravity="left|top"
android:background="#ffffff" />
<View
android:id="@+id/boundary"
android:layout_width="match_parent"
android:layout_height="2sp"
android:background="@color/colorAccent"
android:layout_below="@id/custom_view"/>
<ImageView
android:id="@+id/image"
android:layout_width="300sp"
android:layout_height="300sp"
android:src="@drawable/ic_launcher_background"
android:layout_below="@id/boundary"
android:layout_marginTop="6sp"
android:layout_centerHorizontal="true"/>
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="save"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:onClick="saveImage"/>
</RelativeLayout>
您的MainActivity
public class MainActivity extends AppCompatActivity {
ImageView imageView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = findViewById(R.id.image);
}
public void saveImage(View view) {
View v = findViewById(R.id.custom_view);
int canvasWidth = v.getWidth();
int canvasHeight = v.getHeight();
Bitmap bitmap = Bitmap.createBitmap(canvasWidth, canvasHeight, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
v.draw(canvas);
imageView.setImageBitmap(bitmap);
}
}
- Gopal Dan
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