这几天因为项目需求,需要在ImageView上面叠加一层透明圆弧,并且在沿着圆弧的方向显示相应的文字,效果如下图所示:
images/loading.gif' data-original="http://images2015.cnblogs.com/blog/742015/201605/742015-20160513114909265-1861472364.png" />
拿到这个需求,首先想到的是自定义一个ImageView来实现此功能,即在onDraw()中绘制圆弧和文字。同时因为要保证圆弧的位置可以任意摆放,圆弧的颜色、透明度以及文字大小、颜色等都是可控的,所以增加了一些自定义属性。实现代码非常简单,如下:
1.自定义ImageView:
1 package com.chunk.customviewsdemo.views.ArcImageView; 2 3 import android.content.Context; 4 import android.content.res.TypedArray; 5 import android.graphics.Canvas; 6 import android.graphics.Paint; 7 import android.graphics.Path; 8 import android.graphics.RectF; 9 import android.util.AttributeSet; 10 import android.widget.ImageView; 11 12 import com.chunk.customviewsdemo.R; 13 14 /** 15 * Description:A custom ImageView with circular arc and text 16 * Author: XiaoYu 17 * Date: 2016/5/10 13:55 18 */ 19 public class ArcImageView extends ImageView { 20 /** 21 * The default text size. 22 */ 23 private final float DEFAULT_TEXT_SIZE = 20; 24 /** 25 * The default scale value which decides the width of arc. 26 */ 27 private final float DEFAULT_SCALE = 0.5f; 28 /** 29 * The default transparency of arc. 30 */ 31 private final int DEFAULT_ARC_ALPHA =100; 32 /** 33 * The default width of arc. 34 */ 35 private final int DEFAULT_ARC_WIDTH =160; 36 /** 37 * The default angle that the arc starts with. 38 */ 39 private final int DEFAULT_START_ANGLE = 180; 40 /** 41 * The default angle that the arc. 42 */ 43 private final int DEFAULT_SWEEP_ANGLE = 90; 44 /** 45 * The default distance along the path to add to the text's starting position. 46 */ 47 private final int DEFAULT_H_OFFSET = 100; 48 /** 49 * The default distance above(-) or below(+) the path to position the text. 50 */ 51 private final int DEFAULT_V_OFFSET = 20; 52 private Context mContext; 53 /** 54 * The text displayed on ImageView along arc. 55 */ 56 private String mDrawStr; 57 /** 58 * The font size of text. 59 */ 60 private float mTextSize = DEFAULT_TEXT_SIZE; 61 /** 62 * The scale value which decides the width of arc. 63 */ 64 private float mScale = DEFAULT_SCALE; 65 /** 66 * The transparency of arc. 67 */ 68 private int mArcAlpha = DEFAULT_ARC_ALPHA; 69 /** 70 * The width of arc. 71 */ 72 private int mArcWidth = DEFAULT_ARC_WIDTH; 73 /** 74 * The start angle of angle. 75 */ 76 private int mStartAngle = DEFAULT_START_ANGLE; 77 /** 78 * The swept angle of angle. 79 */ 80 private int mSweepAngle = DEFAULT_SWEEP_ANGLE; 81 /** 82 * The default distance along the path to add to the text's starting position. 83 */ 84 private float mHOffset = DEFAULT_H_OFFSET; 85 /** 86 * The default distance above(-) or below(+) the path to position the text. 87 */ 88 private float mVOffset = DEFAULT_V_OFFSET; 89 /** 90 * The style of arc, all styles includes LEFT_TOP, LEFT_BOTTOM, RIGHT_TOP, RIGHT_BOTTOM, CENTER。 91 * of course, you can add your own style according to your demands. 92 */ 93 private int mDrawStyle; 94 /** 95 * The color of arc. 96 */ 97 private int mArcColor; 98 /** 99 * The color of text.100 */101 private int mTextColor;102 103 public ArcImageView(Context context) {104 super(context);105 this.mContext = context;106 }107 108 public ArcImageView(Context context, AttributeSet attrs) {109 super(context, attrs);110 this.mContext = context;111 obtainAttributes(attrs);112 }113 114 public ArcImageView(Context context, AttributeSet attrs, int defStyleAttr) {115 super(context, attrs, defStyleAttr);116 this.mContext = context;117 obtainAttributes(attrs);118 }119 120 /**121 * Set the text that will be drawn on arc.122 * @param drawStr the text content.123 */124 public void setDrawStr(String drawStr) {125 this.mDrawStr = drawStr;126 //refresh this view127 invalidate();128 }129 130 /**131 * Set the transparency of arc.132 * @param mArcAlpha the value of transparency.133 */134 public void setArcAlpha(int mArcAlpha) {135 this.mArcAlpha = mArcAlpha;136 //refresh this view137 invalidate();138 }139 140 @Override141 protected void onDraw(Canvas canvas) {142 super.onDraw(canvas);143 //draw arc144 Paint arcPaint = new Paint();145 arcPaint.setStrokeWidth(mArcWidth);146 arcPaint.setStyle(Paint.Style.STROKE);147 arcPaint.setColor(mArcColor);148 arcPaint.setAlpha(mArcAlpha);149 int width = getWidth();150 int height = getHeight();151 float radius;152 if (width > height) {153 radius = mScale * height;154 } else {155 radius = mScale * width;156 }157 RectF oval = new RectF();158 159 int center_x = width;160 int center_y = height;161 162 switch (mDrawStyle) {163 case 0:164 center_x = 0;165 center_y = 0;166 mStartAngle = 90;167 mSweepAngle = -90;168 break;169 case 1:170 center_x = 0;171 center_y = height;172 mStartAngle = 270;173 mSweepAngle = 90;174 break;175 case 2:176 center_x = width;177 center_y = 0;178 mStartAngle = 180;179 mSweepAngle = -90;180 break;181 case 3:182 center_x = width;183 center_y = height;184 mStartAngle = 180;185 mSweepAngle = 90;186 break;187 case 4:188 center_x = width / 2;189 center_y = height / 2;190 mStartAngle = 270;191 mSweepAngle = 90;192 break;193 }194 float left = center_x - radius;195 float top = center_y - radius;196 float right = center_x + radius;197 float bottom = center_y + radius;198 oval.set(left, top, right, bottom);199 canvas.drawArc(oval, mStartAngle, mSweepAngle, false, arcPaint);200 201 //draw text202 Paint textPaint = new Paint();203 textPaint.setTextSize(mTextSize);204 textPaint.setStyle(Paint.Style.FILL);205 textPaint.setColor(mTextColor);206 Path path = new Path();207 path.addArc(oval, mStartAngle, mSweepAngle);208 canvas.drawTextOnPath(mDrawStr, path, mHOffset, mVOffset, textPaint);209 }210 211 /**212 * Obtain custom attributes that been defined in attrs.213 * @param attrs A collection of attributes.214 */215 private void obtainAttributes(AttributeSet attrs) {216 TypedArray ta = mContext.obtainStyledAttributes(attrs, R.styleable.ArcImageView);217 mDrawStr = ta.getString(R.styleable.ArcImageView_drawStr);218 mTextSize = ta.getDimension(R.styleable.ArcImageView_textSize, DEFAULT_TEXT_SIZE);219 mArcAlpha = ta.getInteger(R.styleable.ArcImageView_arcAlpha, DEFAULT_ARC_ALPHA);220 mArcWidth = ta.getInteger(R.styleable.ArcImageView_arcWidth, DEFAULT_ARC_WIDTH);221 mStartAngle = ta.getInteger(R.styleable.ArcImageView_startAngle, DEFAULT_START_ANGLE);222 mSweepAngle = ta.getInteger(R.styleable.ArcImageView_startAngle, DEFAULT_SWEEP_ANGLE);223 mHOffset = ta.getInteger(R.styleable.ArcImageView_hOffset, DEFAULT_H_OFFSET);224 mVOffset = ta.getInteger(R.styleable.ArcImageView_vOffset, DEFAULT_V_OFFSET);225 mArcColor = ta.getColor(R.styleable.ArcImageView_arcColor, 0XCCCCCC);226 mTextColor = ta.getColor(R.styleable.ArcImageView_textColor, 0XFFFFFF);227 mDrawStyle = ta.getInt(R.styleable.ArcImageView_drawStyle, 0);228 ta.recycle();229 }230 }
2.在values文件夹下的attrs.
1 <??> 2 <resources> 3 <declare-styleable name="ArcImageView"> 4 <attr name="drawStr" format="string" /> 5 <attr name="textSize" format="dimension" /> 6 <attr name="arcAlpha" format="integer" /> 7 <attr name="arcWidth" format="integer" /> 8 <attr name="startAngle" format="integer" /> 9 <attr name="sweepAngle" format="integer" />10 <attr name="scale" format="float" />11 <attr name="hOffset" format="float" />12 <attr name="vOffset" format="float" />13 <attr name="drawStyle" format="enum">14 <enum name="LEFT_TOP" value="0" />15 <enum name="LEFT_BOTTOM" value="1" />16 <enum name="RIGHT_TOP" value="2" />17 <enum name="RIGHT_BOTTOM" value="3" />18 <enum name="CENTER" value="4" />19 </attr>20 <attr name="arcColor" format="color" />21 <attr name="textColor" format="color" />22 </declare-styleable>23 </resources>
3.在MainActivity调用ArcImageView,实现代码如下:
1 package com.chunk.customviewsdemo; 2 3 import android.os.Bundle; 4 import android.support.v7.app.AppCompatActivity; 5 import android.view.View; 6 import android.widget.Button; 7 8 import com.chunk.customviewsdemo.views.ArcImageView.ArcImageView; 9 10 public class MainActivity extends AppCompatActivity implements View.OnClickListener {11 private ArcImageView aiv_one;12 private ArcImageView aiv_two;13 private ArcImageView aiv_three;14 private ArcImageView aiv_four;15 private Button btn_another_one;16 private int mGroup = 1;17 18 @Override19 protected void onCreate(Bundle savedInstanceState) {20 super.onCreate(savedInstanceState);21 setContentView(R.layout.activity_main);22 aiv_one = (ArcImageView) findViewById(R.id.aiv_one);23 aiv_one.setArcAlpha(180);24 aiv_two = (ArcImageView) findViewById(R.id.aiv_two);25 aiv_two.setArcAlpha(180);26 aiv_three = (ArcImageView) findViewById(R.id.aiv_three);27 aiv_three.setArcAlpha(180);28 aiv_four = (ArcImageView) findViewById(R.id.aiv_four);29 aiv_four.setArcAlpha(180);30 btn_another_one = (Button) findViewById(R.id.btn_another_one);31 btn_another_one.setOnClickListener(this);32 }33 34 @Override35 public void onClick(View v) {36 switch (v.getId()) {37 case R.id.btn_another_one:38 if (mGroup == 1) {39 aiv_one.setDrawStr("苹果");40 aiv_one.setBackgroundResource(R.drawable.apple);41 aiv_two.setDrawStr("柚子");42 aiv_two.setBackgroundResource(R.drawable.pineapple);43 aiv_three.setDrawStr("香蕉");44 aiv_three.setBackgroundResource(R.drawable.banana);45 aiv_four.setDrawStr("菠萝");46 aiv_four.setBackgroundResource(R.drawable.pineapple);47 mGroup = 2;48 } else {49 aiv_one.setDrawStr("牛排");50 aiv_one.setBackgroundResource(R.drawable.steak);51 aiv_two.setDrawStr("海鲜");52 aiv_two.setBackgroundResource(R.drawable.seafood);53 aiv_three.setDrawStr("奶酪");54 aiv_three.setBackgroundResource(R.drawable.cheese);55 aiv_four.setDrawStr("烧烤");56 aiv_four.setBackgroundResource(R.drawable.barbecue);57 mGroup = 1;58 }59 break;60 }61 }62 }
4.MainActivity的布局文件如下:
1 <LinearLayout 2 ="http://schemas.android.com/apk/res/android" 3 ="http://schemas.android.com/apk/res-auto" 4 android:layout_width="match_parent" 5 android:layout_height="match_parent" 6 android:layout_marginTop="100dp" 7 android:layout_marginBottom="100dp" 8 android:orientation="vertical" > 9 10 <Button 11 android:id="@+id/btn_another_one" 12 android:layout_width="wrap_content" 13 android:layout_height="wrap_content" 14 android:text="换一组" /> 15 16 <LinearLayout 17 android:layout_width="match_parent" 18 android:layout_height="0dp" 19 android:layout_weight="1" 20 android:orientation="horizontal" > 21 22 <RelativeLayout 23 android:layout_width="0dp" 24 android:layout_weight="1" 25 android:layout_height="match_parent" > 26 27 <com.chunk.customviewsdemo.views.ArcImageView.ArcImageView 28 android:id="@+id/aiv_one" 29 android:layout_width="match_parent" 30 android:layout_height="match_parent" 31 android:background="@drawable/steak" 32 custom:drawStyle="RIGHT_BOTTOM" 33 custom:drawStr="牛排" 34 custom:arcAlpha="100" 35 custom:arcColor="@color/gray" 36 custom:textColor="@color/black" 37 custom:textSize="20sp" /> 38 </RelativeLayout> 39 40 <RelativeLayout 41 android:layout_width="0dp" 42 android:layout_weight="1" 43 android:layout_height="match_parent" > 44 45 <com.chunk.customviewsdemo.views.ArcImageView.ArcImageView 46 android:id="@+id/aiv_two" 47 android:layout_width="match_parent" 48 android:layout_height="match_parent" 49 android:background="@drawable/seafood" 50 custom:drawStyle="LEFT_BOTTOM" 51 custom:drawStr="海鲜" 52 custom:arcAlpha="100" 53 custom:arcColor="@color/gray" 54 custom:textColor="@color/black" 55 custom:textSize="20sp" /> 56 57 </RelativeLayout> 58 </LinearLayout> 59 60 <LinearLayout 61 android:layout_width="match_parent" 62 android:layout_height="0dp" 63 android:layout_weight="1" 64 android:orientation="horizontal" > 65 66 <RelativeLayout 67 android:layout_width="0dp" 68 android:layout_weight="1" 69 android:layout_height="match_parent" > 70 71 <com.chunk.customviewsdemo.views.ArcImageView.ArcImageView 72 android:id="@+id/aiv_three" 73 android:layout_width="match_parent" 74 android:layout_height="match_parent" 75 android:background="@drawable/cheese" 76 custom:drawStyle="RIGHT_TOP" 77 custom:drawStr="奶酪" 78 custom:arcAlpha="100" 79 custom:arcColor="@color/gray" 80 custom:textColor="@color/black" 81 custom:textSize="20sp" /> 82 </RelativeLayout> 83 84 <RelativeLayout 85 android:layout_width="0dp" 86 android:layout_weight="1" 87 android:layout_height="match_parent" > 88 89 <com.chunk.customviewsdemo.views.ArcImageView.ArcImageView 90 android:id="@+id/aiv_four" 91 android:layout_width="match_parent" 92 android:layout_height="match_parent" 93 android:background="@drawable/barbecue" 94 custom:drawStyle="LEFT_TOP" 95 custom:drawStr="烧烤" 96 custom:arcAlpha="100" 97 custom:arcColor="@color/gray" 98 custom:textColor="@color/black" 99 custom:textSize="20sp" />100 101 </RelativeLayout>102 </LinearLayout>103 </LinearLayout>
注意,在布局文件中引入自定义属性时需要加入一行代码:
好了,需求搞定,剩下的就是搬到实际的项目当中去了。实现效果如下:
总结一下,自定义View一般就是通过重写onDraw、onMeasure()、onLayout()等方法来进行测量、绘制,绘制的时候一般会用到Canvas、Paint、Bitmap等类,测量和绘制的过程其实就是对现实生活中绘图工作的抽象和实现,我们利用面向对象的思想将画板、画纸、画笔等工具以及绘画的动作用一行行代码加以描述就OK啦!
由于实现过程比较简单,我就不贴源码了,大家如果对2D绘图还不是很了解,可以去搜一下相关资料或查阅相关书籍!
原标题:Android打造带透明圆弧的ImageView
关键词:Android