Android入门户十四篇之画图_Android

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。

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

在ImageView上画图以及绘字

直接在控件背景上画图

main.xml的源码：

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<?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>??

程序的源码：

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package?com.testDraw;??
??
import?android.app.Activity;??
import?android.content.res.Resources;??
import?android.graphics.Bitmap;??
import?android.graphics.Bitmap.Config;??
import?android.graphics.BitmapFactory;??
import?android.graphics.Canvas;??
import?android.graphics.Color;??
import?android.graphics.Paint;??
import?android.graphics.Typeface;??
import?android.graphics.drawable.BitmapDrawable;??
import?android.graphics.drawable.Drawable;??
import?android.os.Bundle;??
import?android.view.View;??
import?android.widget.Button;??
import?android.widget.ImageView;??
??
public?class?testDraw?extends?Activity?{??
??????
????ImageView?iv;??
????Button?btn1,btn2,btn3,btn4;??
????Resources?r;??
????@Override??
????public?void?onCreate(Bundle?savedInstanceState)?{??
????????super.onCreate(savedInstanceState);??
????????setContentView(R.layout.main);??
????????iv=(ImageView)this.findViewById(R.id.ImageView01);??
????????btn1=(Button)this.findViewById(R.id.Button01);??
????????btn2=(Button)this.findViewById(R.id.Button02);??
????????btn3=(Button)this.findViewById(R.id.Button03);??
??
????????btn1.setOnClickListener(new?ClickEvent());??
????????btn2.setOnClickListener(new?ClickEvent());??
????????btn3.setOnClickListener(new?ClickEvent());??
??????????
????????r?=?this.getResources();??
??
????
????}??
????class?ClickEvent?implements?View.OnClickListener?{??
??
????????public?void?onClick(View?v)?{??
????????????if(v==btn1)//显示资源图片??
????????????{//功能等效??
????????????????//iv.setBackgroundResource(R.drawable.icon);//打开资源图片??
????????????????Bitmap?bmp=BitmapFactory.decodeResource(r,?R.drawable.icon);//打开资源图片??
????????????????iv.setImageBitmap(bmp);??
????????????}??
????????????else?if(v==btn2)//显示并绘画资源图片??
????????????{??
????????????????Bitmap?bmp=BitmapFactory.decodeResource(r,?R.drawable.icon);//只读,不能直接在bmp上画??
????????????????Bitmap?newb?=?Bitmap.createBitmap(?300,?300,?Config.ARGB_8888?);??
??????????????????
????????????????Canvas?canvasTemp?=?new?Canvas(?newb?);??
????????????????canvasTemp.drawColor(Color.TRANSPARENT);??
??????????????????
????????????????Paint?p?=?new?Paint();??
????????????????String?familyName?="宋体";??
????????????????Typeface?font?=?Typeface.create(familyName,Typeface.BOLD);??
????????????????p.setColor(Color.RED);??
????????????????p.setTypeface(font);??
????????????????p.setTextSize(22);??
????????????????canvasTemp.drawText("写字。。。",50,50,p);??
????????????????canvasTemp.drawBitmap(bmp,?50,?50,?p);//画图??
????????????????iv.setImageBitmap(newb);??
????????????}??
????????????else?if(v==btn3)//直接在Button上绘图??
????????????{??
????????????????Bitmap?newb?=?Bitmap.createBitmap(?btn3.getWidth(),?btn3.getHeight(),?Config.ARGB_8888?);??
????????????????Canvas?canvasTemp?=?new?Canvas(?newb?);??
????????????????canvasTemp.drawColor(Color.WHITE);??
????????????????Paint?p?=?new?Paint();??
????????????????String?familyName?=?"宋体";??
????????????????Typeface?font?=?Typeface.create(familyName,?Typeface.BOLD);??
????????????????p.setColor(Color.RED);??
????????????????p.setTypeface(font);??
????????????????p.setTextSize(20);??
????????????????canvasTemp.drawText("写字。。。",?30,?30,?p);??
????????????????Drawable?drawable?=?new?BitmapDrawable(newb);??
????????????????btn3.setBackgroundDrawable(drawable);??
????????????}??
????????}??
??????????
????}??
??
}?