本文小编为大家详细介绍“怎么自定义视图view使用Canvas实现手写板和涂鸦功能”，内容详细，步骤清晰，细节处理妥当，希望这篇“怎么自定义视图view使用Canvas实现手写板和涂鸦功能”文章能帮助大家解决疑惑，下面跟着小编的思路慢慢深入，一起来学习新知识吧。
预览图
一、xml布局
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/activity_main" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <LinearLayout android:id="@+id/main_linlayout" android:layout_width="match_parent" android:layout_height="300dp" android:orientation="vertical"> </LinearLayout> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal"> <Button android:id="@+id/bt" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="1" android:text="确定"/> <Button android:id="@+id/bt_clear" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="1" android:text="清空"/> </LinearLayout> <ImageView android:id="@+id/img" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="5dp" android:layout_gravity="center"/> </LinearLayout>
布局预览图
二、MainActivity代码
package tester.ermu.com.handdrawdemo;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BlurMaskFilter;
import android.graphics.EmbossMaskFilter;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;
public class MainActivity extends Activity implements View.OnClickListener{
EmbossMaskFilter emboss;
BlurMaskFilter blur;
DrawView drawView;
private LinearLayout main_linlayout;
private Button bt,bt_clear;
private ImageView img;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
init(); //初始化组件
getWH();//获取我们xml布局中view的宽高
}
//获取我们xml布局中view的宽高
private void getWH() {
// 获取创建的宽度和高度
DisplayMetrics displayMetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getRealMetrics(displayMetrics);
// 创建一个DrawView，该DrawView的宽度、高度与该Activity保持相同
main_linlayout = (LinearLayout)findViewById(R.id.main_linlayout);
drawView = new DrawView(this, displayMetrics.widthPixels, displayMetrics.heightPixels);
main_linlayout.addView(drawView);
drawView.requestFocus();
}
private void init() {
bt = (Button)findViewById(R.id.bt);
bt.setOnClickListener(this);
bt_clear = (Button)findViewById(R.id.bt_clear);
bt_clear.setOnClickListener(this);
img = (ImageView) findViewById(R.id.img);
}
@Override
public void onClick(View v) {
switch (v.getId()){
case R.id.bt:
Bitmap bit = drawView.getPaintBitmap();
img .setImageBitmap(bit);
break;
case R.id.bt_clear:
drawView.clear();
break;
}
}
}三、我们自定义view的类
package tester.ermu.com.handdrawdemo;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PorterDuff;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
public class DrawView extends View {
// 定义记录前一个拖动事件发生点的坐标
float preX;
float preY;
private Path path;
public Paint paint = null;
// 定义一个内存中的图片，该图片将作为缓冲区
Bitmap cacheBitmap = null;
// 定义cacheBitmap上的Canvas对象
Canvas cacheCanvas = null;
public DrawView(Context context) {
super(context);
}
public DrawView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public DrawView(Context context, int width , int height) {
super(context);
// 创建一个与该View相同大小的缓存区
cacheBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
cacheCanvas = new Canvas();
path = new Path();
// 设置cacheCanvas将会绘制到内存中的cacheBitmap上
cacheCanvas.setBitmap(cacheBitmap);
// 设置画笔的颜色
paint = new Paint(Paint.DITHER_FLAG);
paint.setColor(Color.RED);
// 设置画笔风格
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(3);
// 反锯齿
paint.setAntiAlias(true);
paint.setDither(true);
}
@Override
public boolean onTouchEvent(MotionEvent event)
{
// 获取拖动事件的发生位置
float x = event.getX();
float y = event.getY();
switch (event.getAction())
{
case MotionEvent.ACTION_DOWN:
// 从前一个点绘制到当前点之后，把当前点定义成下次绘制的前一个点
path.moveTo(x, y);
preX = x;
preY = y;
break;
case MotionEvent.ACTION_MOVE:
// 从前一个点绘制到当前点之后，把当前点定义成下次绘制的前一个点
path.quadTo(preX, preY, x, y);
preX = x;
preY = y;
break;
case MotionEvent.ACTION_UP:
cacheCanvas.drawPath(path, paint); // ①
path.reset();
break;
}
invalidate();
// 返回true表明处理方法已经处理该事件
return true;
}
@Override
public void onDraw(Canvas canvas)
{
Paint bmpPaint = new Paint();
// 将cacheBitmap绘制到该View组件上
canvas.drawBitmap(cacheBitmap, 0, 0, bmpPaint); // ②
// 沿着path绘制
canvas.drawPath(path, paint);
}
//获取我们绘制成功后的图片
public Bitmap getPaintBitmap() {
return resizeImage(cacheBitmap, 620, 780);
}
// 缩放
public static Bitmap resizeImage(Bitmap bitmap, int width, int height) {
//获取图片的宽高
int originWidth = bitmap.getWidth();
int originHeight = bitmap.getHeight();
//这里缩放我们的尺寸，缩放多少自己去定义
float scaleWidth = ((float) width) / originWidth;
float scaleHeight = ((float) height) / originHeight;
//进行缩放
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
Bitmap resizedBitmap = Bitmap.createBitmap(bitmap, 0, 0, originWidth,
originHeight, matrix, true);
return resizedBitmap;
}
//清除画板
public void clear() {
if (cacheBitmap != null) {
path.reset();
cacheCanvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
invalidate();
}
}
}