Android入门第十四篇之画图

常用控件说了不少，现在说说手机开发中也常用到的画图。要掌握Android的画图，首先就要了解一下，基本用到的图形接口：

1.Bitmap，可以来自资源/文件，也可以在程序中创建，实际上的功能相当于图片的存储空间；

2.Canvas，紧密与Bitmap联系，把Bitmap比喻内容的话，那么Canvas就是提供了众多方法操作Bitamp的平台；

3.Paint，与Canvas紧密联系，是"画板"上的笔刷工具，也用于设置View控件上的样式；?

4.Drawable，如果说前三者是看不见地在内存中画图，那么Drawable就是把前三者绘图结果表现出来的接口。Drawable多个子类，例如：位图(BitmapDrawable)、图形(ShapeDrawable)、图层(LayerDrawable)等。

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本文主要讲解如何在ImageView画图，以及如何直接在Button(继承View的控件)上面绘制自定义图像。

直接把资源图片画出来

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在ImageView上画图以及绘字

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直接在控件背景上画图

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main.xml的源码：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" ><Button android:id="@+id/Button01" android:layout_width="fill_parent" android:layout_height="44px" android:text="显示资源图片"></Button><Button android:id="@+id/Button02" android:layout_width="fill_parent" android:layout_height="44px" android:text="显示并绘画资源图片"></Button><Button android:id="@+id/Button03" android:layout_height="44px" android:layout_width="fill_parent" android:text="在控件上绘图"></Button><ImageView android:id="@+id/ImageView01" android:layout_width="wrap_content" android:layout_height="wrap_content"></ImageView></LinearLayout>

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程序的源码：

?view plaincopy to clipboardprint?

1. package?com.testDraw;????
2. import?android.app.Activity;??import?android.content.res.Resources;??
3. import?android.graphics.Bitmap;??import?android.graphics.Bitmap.Config;??
4. import?android.graphics.BitmapFactory;??import?android.graphics.Canvas;??
5. import?android.graphics.Color;??import?android.graphics.Paint;??
6. import?android.graphics.Typeface;??import?android.graphics.drawable.BitmapDrawable;??
7. import?android.graphics.drawable.Drawable;??import?android.os.Bundle;??
8. import?android.view.View;??import?android.widget.Button;??
9. import?android.widget.ImageView;????
10. public?class?testDraw?extends?Activity?{????????
11. ????ImageView?iv;??????Button?btn1,btn2,btn3,btn4;??
12. ????Resources?r;??????@Override??
13. ????public?void?onCreate(Bundle?savedInstanceState)?{??????????super.onCreate(savedInstanceState);??
14. ????????setContentView(R.layout.main);??????????iv=(ImageView)this.findViewById(R.id.ImageView01);??
15. ????????btn1=(Button)this.findViewById(R.id.Button01);??????????btn2=(Button)this.findViewById(R.id.Button02);??
16. ????????btn3=(Button)this.findViewById(R.id.Button03);????
17. ????????btn1.setOnClickListener(new?ClickEvent());??????????btn2.setOnClickListener(new?ClickEvent());??
18. ????????btn3.setOnClickListener(new?ClickEvent());????????????
19. ????????r?=?this.getResources();????
20. ????????}??
21. ????class?ClickEvent?implements?View.OnClickListener?{????
22. ????????public?void?onClick(View?v)?{??????????????if(v==btn1)//显示资源图片??
23. ????????????{//功能等效??????????????????//iv.setBackgroundResource(R.drawable.icon);//打开资源图片??
24. ????????????????Bitmap?bmp=BitmapFactory.decodeResource(r,?R.drawable.icon);//打开资源图片??????????????????iv.setImageBitmap(bmp);??
25. ????????????}??????????????else?if(v==btn2)//显示并绘画资源图片??
26. ????????????{??????????????????Bitmap?bmp=BitmapFactory.decodeResource(r,?R.drawable.icon);//只读,不能直接在bmp上画??
27. ????????????????Bitmap?newb?=?Bitmap.createBitmap(?300,?300,?Config.ARGB_8888?);????????????????????
28. ????????????????Canvas?canvasTemp?=?new?Canvas(?newb?);??????????????????canvasTemp.drawColor(Color.TRANSPARENT);??
29. ??????????????????????????????????Paint?p?=?new?Paint();??
30. ????????????????String?familyName?="宋体";??????????????????Typeface?font?=?Typeface.create(familyName,Typeface.BOLD);??
31. ????????????????p.setColor(Color.RED);??????????????????p.setTypeface(font);??
32. ????????????????p.setTextSize(22);??????????????????canvasTemp.drawText("写字。。。",50,50,p);??
33. ????????????????canvasTemp.drawBitmap(bmp,?50,?50,?p);//画图??????????????????iv.setImageBitmap(newb);??
34. ????????????}??????????????else?if(v==btn3)//直接在Button上绘图??
35. ????????????{??????????????????Bitmap?newb?=?Bitmap.createBitmap(?btn3.getWidth(),?btn3.getHeight(),?Config.ARGB_8888?);??
36. ????????????????Canvas?canvasTemp?=?new?Canvas(?newb?);??????????????????canvasTemp.drawColor(Color.WHITE);??
37. ????????????????Paint?p?=?new?Paint();??????????????????String?familyName?=?"宋体";??
38. ????????????????Typeface?font?=?Typeface.create(familyName,?Typeface.BOLD);??????????????????p.setColor(Color.RED);??
39. ????????????????p.setTypeface(font);??????????????????p.setTextSize(20);??
40. ????????????????canvasTemp.drawText("写字。。。",?30,?30,?p);??????????????????Drawable?drawable?=?new?BitmapDrawable(newb);??
41. ????????????????btn3.setBackgroundDrawable(drawable);??????????????}??
42. ????????}????????????
43. ????}????
44. }?