Android Studio——简单绘图板

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：