Android Studio怎么实现简单绘图板

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目的

设计一个手绘图形的画板

工具及环境

使用java语言，在Android studio平台上进行开发

功能设计

实现一个可以绘图的画板，界面有相关的选择按钮。可以根据按钮切换画笔的颜色，刷子可以加粗画笔的线条大小，橡皮可以用于抹除已经绘制的图案，清屏可实现清屏重置画板

设计思路

首先设计界面，然后设计按钮点击功能。橡皮擦的功能可通过把画笔颜色设置与背景颜色一致来实现，清屏功能可通过背景重置覆盖原背景实现

代码

activity_main.xml

HandWrite.java

package com.xdw.exercise; import android.content.Context;import android.graphics.*;import android.graphics.Paint.Style;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View; public class HandWrite extends View{    Paint paint = null;    Bitmap originalBitmap = null;    Bitmap new1_Bitmap = null;    Bitmap new2_Bitmap = null;    float startX = 0,startY = 0;    float clickX = 0,clickY = 0;    boolean isMove = true;    boolean isClear = false;    int color=Color.BLUE;    float strokeWidth=10.0f;    public HandWrite(Context context, AttributeSet attrs)    {        super(context, attrs);        originalBitmap = BitmapFactory                .decodeResource(getResources(), R.drawable.iv).copy(Bitmap.Config.ARGB_8888,true);        new1_Bitmap = Bitmap.createBitmap(originalBitmap);    }    public void clear(){        isClear = true;        new2_Bitmap = Bitmap.createBitmap(originalBitmap);        invalidate();    }     public void red(){        isClear=false;        color=Color.RED;    }     public void blue(){        isClear=false;        color=Color.BLUE;    }    public void brush(){        strokeWidth=20.0f;    }    public void eraser(){        color=Color.WHITE;        strokeWidth=80.0f;    }     @Override    protected void onDraw(Canvas canvas)    {        super.onDraw(canvas);        canvas.drawBitmap(HandWriting(new1_Bitmap), 0, 0,null);    }    public Bitmap HandWriting(Bitmap o_Bitmap)    {        Canvas canvas = null;        if(isClear) {        canvas = new Canvas(new2_Bitmap);    }       else{        canvas = new Canvas(o_Bitmap);    }        paint = new Paint();        paint.setStyle(Style.STROKE);        paint.setAntiAlias(true);        paint.setColor(color);        paint.setStrokeWidth(strokeWidth);        if(isMove)        {            canvas.drawLine(startX, startY, clickX, clickY, paint);        }        startX = clickX;        startY = clickY;        if(isClear)        {            return new2_Bitmap;        }        return o_Bitmap;    }      @Override    public boolean onTouchEvent(MotionEvent event)    {        clickX = event.getX();        clickY = event.getY();        if(event.getAction() == MotionEvent.ACTION_DOWN)        {            isMove = false;            invalidate();            return true;        }        else if(event.getAction() == MotionEvent.ACTION_MOVE)        {            isMove = true;            invalidate();            return true;        }        return super.onTouchEvent(event);    }}

MainActivity.java

package com.xdw.exercise; import android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button; public class MainActivity extends Activity {    private HandWrite handWrite = null;    Button red,blue,clear,brush,eraser;     @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        handWrite = (HandWrite) findViewById(R.id.handwriteview);        red =(Button)findViewById(R.id.red);        blue=(Button)findViewById(R.id.blue);        clear = (Button) findViewById(R.id.clear);        brush=(Button)findViewById(R.id.brush);        eraser=(Button)findViewById(R.id.eraser);        clear.setOnClickListener(new cClick());        red.setOnClickListener(new rClick());        blue.setOnClickListener(new bClick());        brush.setOnClickListener(new brClick());        eraser.setOnClickListener(new eClick());     }      class cClick implements OnClickListener {        public void onClick(View v) {            handWrite.clear();        }    }    class rClick implements OnClickListener {        public void onClick(View v) {            handWrite.red();        }    }    class bClick implements OnClickListener {        public void onClick(View v) {            handWrite.blue();        }    }    class brClick implements OnClickListener {        public void onClick(View v) {            handWrite.brush();        }    }    class eClick implements OnClickListener {        public void onClick(View v) {            handWrite.eraser();        }    }}

效果显示：

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