Android-Compass(罗盘)详解

Compass(罗盘) 详解

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本文地址: http://blog.csdn.net/caroline_wendy/article/details/21379067

Compass(罗盘)是一个定制的视图, 继承View类, 重写了视图的边界(onMeasure)和内容(onDraw);

如图:

以下是Compass的具体设计:

1. 创建CompassView类, 罗盘视图

位置: java->package->CompassView

package mzx.spike.compass.app;  import android.content.Context; import android.content.res.Resources; import android.graphics.Canvas; import android.graphics.Paint; import android.util.AttributeSet; import android.view.View; import android.view.accessibility.AccessibilityEvent;  /**  * Created by C.L.Wang on 14-3-16.  */ public class CompassView extends View {      private float bearing; //方位      public void setBearing(float _bearing) {         bearing = _bearing;         sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_TEXT_CHANGED);     }      public float getBearing() {         return bearing;     }      private Paint markerPaint;     private Paint textPaint;     private Paint circlePaint;     private String northString;     private String eastString;     private String southString;     private String westString;     private int textHeight;      public CompassView(Context context) {         super(context);         initCompassView();     }      public CompassView(Context context, AttributeSet attrs) {         super(context, attrs);         initCompassView();     }      public CompassView(Context context, AttributeSet attrs, int defaultStyle) {         super(context, attrs, defaultStyle);         initCompassView();     }      private void initCompassView() {         setFocusable(true);          Resources r = this.getResources();          circlePaint = new Paint(Paint.ANTI_ALIAS_FLAG);         circlePaint.setColor(r.getColor(R.color.background_color));         circlePaint.setStrokeWidth(1); //笔画宽度         circlePaint.setStyle(Paint.Style.FILL_AND_STROKE);          northString = r.getString(R.string.cardinal_north);         eastString = r.getString(R.string.cardinal_east);         southString = r.getString(R.string.cardinal_south);         westString = r.getString(R.string.cardinal_west);          textPaint = new Paint(Paint.ANTI_ALIAS_FLAG);         textPaint.setColor(r.getColor(R.color.text_color));          textHeight = (int)textPaint.measureText("yY");          markerPaint = new Paint(Paint.ANTI_ALIAS_FLAG);         markerPaint.setColor(r.getColor(R.color.marker_color));     }      @Override     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {         int measuredWidth = measure(widthMeasureSpec);         int measuredHeight = measure(heightMeasureSpec);          int d = Math.min(measuredWidth, measuredHeight);          setMeasuredDimension(d, d);     }      protected int measure(int measureSpec) {         int result;          int specMode = MeasureSpec.getMode(measureSpec);         int specSize = MeasureSpec.getSize(measureSpec);          if (specMode == MeasureSpec.UNSPECIFIED) {             result = 200;         } else {             result = specSize;         }          return result;     }      @Override     protected void onDraw(Canvas canvas) {         int mMeasuredWidth = getMeasuredWidth();         int mMeasuredHeight = getMeasuredHeight();          int px = mMeasuredWidth/2;         int py = mMeasuredHeight/2;          int radius = Math.min(px, py);          canvas.drawCircle(px, py, radius, circlePaint);          canvas.save();         canvas.rotate(-bearing, px, py); //相反方向旋转          int textWidth = (int)textPaint.measureText("W");         int cardinalX = px-textWidth/2;         int cardinalY = py-radius+textHeight;          for (int i=0; i<24; i++) {             canvas.drawLine(px, py-radius, px, py-radius+10, markerPaint);              canvas.save();             canvas.translate(0, textHeight);              if (i%6 == 0) {                 String dirString = "";                 switch (i) {                     case (0) : {                         dirString = northString;                         int arrowY = 2*textHeight;                         canvas.drawLine(px, arrowY, px-5, 3*textHeight, markerPaint);                         canvas.drawLine(px, arrowY, px+5, 3*textHeight, markerPaint);                         break;                     }                      case (6) : dirString = eastString; break;                     case (12) : dirString = southString; break;                     case (18) : dirString = westString; break;                 }                  canvas.drawText(dirString, cardinalX, cardinalY, textPaint);             }              else if (i%3 == 0) {                 String angle = String.valueOf(i*15);                 float angleTextWidth = textPaint.measureText(angle);                  int angleTextX = (int)(px-angleTextWidth/2);                 int angleTextY = py-radius+textHeight;                 canvas.drawText(angle, angleTextX, angleTextY, textPaint);             }              canvas.restore();              canvas.rotate(15, px, py);         }         canvas.restore();     }      @Override     public boolean dispatchPopulateAccessibilityEvent(final AccessibilityEvent event) {         super.dispatchPopulateAccessibilityEvent(event);          if (isShown()) {             String bearingStr = String.valueOf(bearing);              event.getText().add(bearingStr);              return true;         } else             return false;     } }

这个类代码较多, 详解:

1. 私有变量bearing, 罗盘的方位, 包含set()和get()方法, 唯一可以操作的参数;

2. 资源的私有变量, 表示图画, 字符串, 高度, 从资源(xml)中获得;

3. 重载构造函数, 添加初始化资源程序initCompassView();

4. 在初始化程序initCompassView()中, 使用资源表的引用(getResources),初始化资源变量;

5. 重写onMeasure()方法, 创建边界, 使用setMeasuredDimension确定边界;

6. 在方法measure中, 具体的边界实现;

7. 重写onDraw()方法, 绘制图像;

8. onDraw(), 绘制: 圆形(drawCircle), 旋转(rotate), 24个线, 4个字母, 4个度数, 小箭头;

9. 注意set()方法中的sendAccessibilityEvent广播访问事件, 重写dispatchPopulateAccessibilityEvent方法, 接受广播事件, 改变应用程序的状态;

10. set方法可以定制旋转的角度;

2. 修改资源文件, 颜色(colors.xml)和字符串(strings.xml)

位置: res->values->colors&strings

      #F555     #AFFF     #AFFF 

       Compass     Settings     N     E     S     W   

3. 修改主布局文件(activity_main.xml)

位置: res->layout->activity_main.xml

4. 修改主Activity的实现(MainActivity.java)

位置: java->package->MainActivity.java

......     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         CompassView cv = (CompassView)this.findViewById(R.id.compassView);         cv.setBearing(45);     } ......

5. 执行程序:

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