Bitmap绘图

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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;@Overrideprotected 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@Overridepublic void onClick(View v) {Mydraw.drawLine(mImageView);Mydraw.drawText(mImageView);Mydraw.drawPic(mImageView, getResources());}}

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