Android中Canvas绘图方法的实现
16lz
2021-01-23
Android中2D图形可以使用Canvas来实现，我们可以通过重写View.onDraw()方法来实现Canvas对象。
常用方法
| drawBitmap() | 绘制位图 |
| drawCircle() | 绘制圆形 |
| drawColor() | 绘制填充画布颜色 |
| drawLine() | 绘制直线 |
| drawPath() | 绘制路径 |
| drawPoint() | 绘制点 |
| drawRect() | 绘制矩形 |
| drawText() | 绘制文字 |
最终效果
创建项目
实现代码
MainActivity.java
package com.lujie.canvasdemo;import android.app.Activity;import android.os.Bundle;import android.util.DisplayMetrics;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.Button;import android.widget.LinearLayout;public class MainActivity extends Activity {private LinearLayout layout;private Button button_drawLine;private Button button_drawCircle;private Button button_drawRect;private Button button_dark;private Button button_drawPoint;private Button button_drawLogo;private Button button_drawText;private Button button_autoDraw;private boolean flag = false; protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initUI(); } private void initUI() { layout = (LinearLayout) findViewById(R.id.linearLayout_main); button_drawLine = (Button) findViewById(R.id.button_drawLine); button_drawCircle = (Button) findViewById(R.id.button_drawCircle); button_drawRect = (Button) findViewById(R.id.button_drawRect); button_dark = (Button) findViewById(R.id.button_dark); button_drawPoint = (Button) findViewById(R.id.button_drawPoint); button_drawLogo = (Button) findViewById(R.id.button_drawLogo); button_drawText = (Button) findViewById(R.id.button_drawText); button_autoDraw = (Button) findViewById(R.id.button_autoDraw); final MyView view = new MyView(this); DisplayMetrics display = new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(display); int width = display.widthPixels; view.setMinimumWidth(width); view.setMinimumHeight(width); view.setWidth(width); layout.addView(view); button_drawLine.setOnClickListener(new View.OnClickListener() {public void onClick(View v) {view.setDrawType(1);view.invalidate();}}); button_drawCircle.setOnClickListener(new View.OnClickListener() {public void onClick(View v) {view.setDrawType(2);view.invalidate();}}); button_drawRect.setOnClickListener(new View.OnClickListener() {public void onClick(View v) {view.setDrawType(3);view.invalidate();}}); button_dark.setOnClickListener(new View.OnClickListener() {public void onClick(View v) {view.setDrawType(4);view.invalidate();}}); button_drawPoint.setOnClickListener(new View.OnClickListener() {public void onClick(View v) {view.setDrawType(5);view.invalidate();}}); button_drawLogo.setOnClickListener(new View.OnClickListener() {public void onClick(View v) {view.setDrawType(6);view.invalidate();}}); button_drawText.setOnClickListener(new View.OnClickListener() {public void onClick(View v) {view.setDrawType(7);view.invalidate();}}); button_autoDraw.setOnClickListener(new View.OnClickListener() {public void onClick(View v) {if(flag)view.stopDraw();elseview.autoDraw();flag = !flag;}}); }}
MyView.java
package com.lujie.canvasdemo;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Path;import android.graphics.Rect;import android.view.View;public class MyView extends View{private int width;private int drawType = -1;private Thread thread = null;private boolean flag = false;public MyView(Context context) {super(context);}public void setWidth(int width) {this.width = width;}public void setDrawType(int drawType) {this.drawType = drawType;}public void autoDraw() {flag = true;thread = new Thread() {public void run() {for(drawType = 1; flag; drawType++) {if(drawType > 7) {drawType = 1;}setDrawType(drawType);postInvalidate();try {Thread.sleep(1000);}catch(InterruptedException e) {e.printStackTrace();}}}};thread.start();}public void stopDraw() {flag = false;}protected void onDraw(Canvas canvas) {Paint paint = new Paint();paint.setAntiAlias(true);paint.setColor(Color.rgb(255,255,215));canvas.drawRect(new Rect(0, 0, width, width), paint);switch(drawType) {case 1:paint.setColor(Color.CYAN);canvas.drawLine(50, 50, 180, 180, paint);break;case 2:paint.setColor(Color.RED);canvas.drawCircle(width/2, width/2, 50, paint);break;case 3:paint.setColor(Color.rgb(85,99,200));canvas.drawRect(50, 50, 150, 120, paint);break;case 4:canvas.drawColor(Color.rgb(235,235,195));break;case 5:paint.setColor(Color.rgb(55,55,99));canvas.drawPoint(50, 50, paint);canvas.drawPoint(60, 50, paint);canvas.drawPoint(70, 50, paint);canvas.drawPoint(80, 50, paint);canvas.drawPoint(80, 55, paint);canvas.drawPoint(80, 60, paint);canvas.drawPoint(80, 65, paint);canvas.drawPoint(80, 70, paint);canvas.drawPoint(80, 75, paint);canvas.drawPoint(90, 50, paint);canvas.drawPoint(100, 50, paint);canvas.drawPoint(110, 50, paint);break;case 6:paint.setColor(Color.rgb(208,135,68));paint.setAntiAlias(true);float scale = 1.8f;Path path1 = new Path();path1.moveTo(120*scale, 30*scale);path1.lineTo(40*scale, 22*scale);path1.lineTo(30*scale, 30*scale);path1.lineTo(40*scale, 38*scale);path1.close();canvas.drawPath(path1, paint);Path path2 = new Path();path2.moveTo(120*scale, 55*scale);path2.lineTo(40*scale, 47*scale);path2.lineTo(30*scale, 55*scale);path2.lineTo(40*scale, 63*scale);path2.close();canvas.drawPath(path2, paint);Path path3 = new Path();path3.moveTo(120*scale, 80*scale);path3.lineTo(40*scale, 72*scale);path3.lineTo(30*scale, 80*scale);path3.lineTo(40*scale, 88*scale);path3.close();canvas.drawPath(path3, paint);Path path4 = new Path();path4.moveTo(35*scale, 20*scale);path4.lineTo(35*scale, 90*scale);path4.lineTo(20*scale, 85*scale);path4.lineTo(20*scale, 25*scale);path4.close();canvas.drawPath(path4, paint);break;case 7:paint.setColor(Color.rgb(88, 210, 64));paint.setTextSize(40);canvas.drawText("天天开心", 40, width/2, paint);break;}}}
activity_main.xml
参考文档
http://www.android-doc.com/reference/android/graphics/Canvas.html
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