Android的画布通过手指画 [英] Android Canvas Draw by finger

问题描述

在一个项目，我的工作在我现在的工作，我已经遇到了一些非常致命的问题，其中有两种

On a project I’m working on at my current job, I’ve come across some really pernicious problems where there is either

no good information available or
the good information is buried under a sea of bad information.

我已经把这些问题，现在这些问题都解决了，我打算与所有开发人员共享一个简单的例子......

I’ve kept these issues and, now the issues are resolved, I plan to share a simple example with all developers...

为了手指的触摸和运动事件，并提请 我希望我的回答能帮助大家。您可以根据自己的需要以下修改.....：）

To get the touch and motion event of finger and draw I hope my answer would help you all.. You can modify the below according to your needs..... :)

推荐答案

按照以下步骤操作：

1）创建视图类，然后扩展视图，同时创建构造

1) Create a view class then extends View, Also create constructor

覆盖的OnDraw（）。你加在哪里手指触摸和移动路径。你重写的这一目的onTouch（）。在你的的OnDraw（）你画使用您所选择的油漆的路径。你应该叫无效（）刷新视图。

override the onDraw(). You add the path of where finger touches and moves. You override the onTouch() of this purpose. In your onDraw() you draw the paths using the paint of your choice. You should call invalidate() to refresh the view.

//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） 您的活动： -

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>

这篇关于Android的画布通过手指画的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！