Bitmap绘图

本文介绍了在bitmap上绘制三种图形，分别是：画线、写文本、画上原本存在 的图片

首先写好布局，代码如下

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:layout_width="300dp"
        android:layout_height="350dp"
        android:layout_centerInParent="true">
        
        <ImageView
            android:id="@+id/id_iv_1"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
        
    </LinearLayout>
    
    <Button
        android:id="@+id/id_bt1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:text="点我"/>
    
    

</RelativeLayout>

第二步，自定义一个工具类Mydraw包含三种方法drawLine()，drawText\()，drawPic()，从字面上很容易理解分别是：画线，写字，画图，代码如下：

public class Mydraw {
	static Bitmap mBitmap;
	public static void drawLine(ImageView view){
		int height=view.getHeight();
		int width=view.getWidth();
		
		mBitmap=Bitmap.createBitmap(width,height,Config.ARGB_8888);
		Canvas mCanvas=new Canvas(mBitmap);
		Paint mPaint=new Paint();
		mPaint.setColor(Color.parseColor("#7B7B7B"));
		mPaint.setStyle(Style.STROKE);
		mPaint.setStrokeWidth(5);
		mCanvas.drawLine(0, 0, width ,0 , mPaint);
		mCanvas.drawLine(width, 0, width ,height , mPaint);
		mCanvas.drawLine(0, 0, 0 ,height , mPaint);
		mCanvas.drawLine(0, height, width, height, mPaint);
		view.setImageBitmap(mBitmap);
	}
	
	public static void drawText(ImageView view){
		String mText="solo你好";
		Rect mRect=new Rect();
		
		int width=view.getWidth();
		int height=view.getHeight();
		
		Canvas mCanvas=new Canvas(mBitmap);
		Paint mPaint=new Paint();
		mPaint.setColor(Color.RED);
		mPaint.setTextSize(40);
		mPaint.getTextBounds(mText, 0, mText.length(), mRect);
		mCanvas.drawText(mText, width/2-mRect.width()/2,height/2+mRect.height()/2, mPaint);
		view.setImageBitmap(mBitmap);
	}
	
	public static void drawPic(ImageView view,Resources res){
		Bitmap bm=BitmapFactory.decodeResource(res,R.drawable.ic_launcher);
		int width=view.getWidth();
		int height=view.getHeight();
		
		Canvas mCanvas=new Canvas(mBitmap);
		mCanvas.drawBitmap(bm, width/2-bm.getWidth()/2, 0, null);
		view.setImageBitmap(mBitmap);
	}
	
}

最后一步，在MianActivity中调用这些方法，代码如下：

public class MainActivity extends Activity implements OnClickListener {

	private ImageView mImageView;
	private Button mButton;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		mImageView=(ImageView) findViewById(R.id.id_iv_1);
		mButton=(Button)findViewById(R.id.id_bt1);
		mButton.setOnClickListener(this);
		
		
	}

	//由于不能再onCreate()中直接测量view的宽和高,所以我们这里在button的点击事件中去执行这些测量
	@Override
	public void onClick(View v) {
		Mydraw.drawLine(mImageView);
		Mydraw.drawText(mImageView);
		Mydraw.drawPic(mImageView, getResources());
		
	}

	
}