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
把
实现文件(app.CompassView), 注册在布局文件中, 指定
ID(compassView);
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); } ......填充视图, 获得资源文件的
引用(findViewById),
设置角度(setBearing);
5. 执行程序:
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