目录

1. 属性文件 res/values/attrs.xml

2. 自定义控件类文件 MyClipbroad.class

3. XML布局文件中的使用

4. Java文件中的使用

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该写字板可设置画笔颜色、画笔宽度、画布背景，具有导出图像、清空画布功能，可与OnTouchListener配合达到触摸绘画的效果。

1. 属性文件 res/values/attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources><declare-styleable name="MyClipboard"><attr name="paintColor" format="color" /><attr name="paintWidth" format="integer" /></declare-styleable>
</resources>

2. 自定义控件类文件 MyClipbroad.class

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.util.Log;
import android.widget.RelativeLayout;import androidx.annotation.Nullable;
import androidx.core.content.ContextCompat;public class MyClipboard extends RelativeLayout {private int viewHeight,viewWidth;private Path path=new Path();private int paintColor=R.color.black;private int paintWidth=5;public MyClipboard(Context context) {super(context);setLayoutParams(new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT,RelativeLayout.LayoutParams.MATCH_PARENT));}@SuppressLint("ResourceAsColor")public MyClipboard(Context context, @Nullable AttributeSet attrs) {super(context, attrs);TypedArray typedArray =context.obtainStyledAttributes(attrs,R.styleable.MyClipboard);paintColor=typedArray.getColor(typedArray.getIndex(R.styleable.MyClipboard_paintColor), ContextCompat.getColor(context,R.color.black));paintWidth=typedArray.getInt(typedArray.getIndex(R.styleable.MyClipboard_paintWidth),5);typedArray.recycle();setLayoutParams(new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT,RelativeLayout.LayoutParams.MATCH_PARENT));}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);viewHeight=MeasureSpec.getSize(heightMeasureSpec);viewWidth=MeasureSpec.getSize(heightMeasureSpec);}@SuppressLint("ResourceAsColor")protected void onDraw(Canvas canvas) {super.dispatchDraw(canvas);Paint paint=new Paint(paintColor);paint.setStrokeWidth(paintWidth);paint.setStyle(Paint.Style.STROKE);canvas.drawPath(path,paint);}/*** 绘制直线* @param x1* @param y1* @param x2* @param y2*/public void draw(float x1,float y1,float x2,float y2){path.moveTo(x1,y1);path.lineTo(x2,y2);invalidate();}/*** 清空图像*/public void cleanDraw(){Log.d("OK","clean");path=new Path();invalidate();}/*** 导出当前图像* @return 位图Bitmap*/public Bitmap getBitmap(){Bitmap bitmap=Bitmap.createBitmap(viewWidth,viewHeight, Bitmap.Config.ARGB_8888);Canvas canvas=new Canvas(bitmap);Paint paint=new Paint(paintColor);paint.setStrokeWidth(paintWidth);paint.setStyle(Paint.Style.STROKE);canvas.drawPath(path,paint);return bitmap;}
}

3. XML布局文件中的使用

请注意一定要设置background属性！

<com.example.clipboard.MyClipboardandroid:id="@+id/myc"android:layout_width="match_parent"android:layout_height="match_parent"app:paintColor="@color/teal_200"app:paintWidth="5"android:background="@color/white"/>

4. Java文件中的使用

//获取控件MyClipboard myClipboard=findViewById(R.id.myc);//添加监听器myClipboard.setOnTouchListener(new View.OnTouchListener() {private float oldX=0,oldY=0;public boolean onTouch(View view, MotionEvent motionEvent) {int action=motionEvent.getAction();if(action==MotionEvent.ACTION_DOWN){oldX=motionEvent.getX();oldY=motionEvent.getY();return true;}else if (action==MotionEvent.ACTION_MOVE) {float newX=motionEvent.getX();float newY=motionEvent.getY();((MyClipboard)view).draw(oldX,oldY,newX,newY);oldX=newX;oldY=newY;return true;}    else if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_CANCEL) {float newX=motionEvent.getX();float newY=motionEvent.getY();((MyClipboard)view).draw(oldX,oldY,newX,newY);oldX=0;oldY=0;return true;}return false;}
});//清空图像
myClipboard.cleanDraw();//导出图像
Bitmap bitmap=myClipboard.getBitmap();

tag：画板；手写板