错误示范：
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页面显示：
gps_view_activity.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:background="@color/satellites_bg" > <TextView android:id="@+id/gps_status_text" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="状态"/> <TextView android:id="@+id/lonlat_text" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="0 0"/> //自定义控件显示卫星分布状态图 <ylybbs.study.mygpstest.SatellitesView android:id="@+id/satellitesView" android:layout_width="match_parent" android:layout_height="fill_parent" /> </LinearLayout>
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自定义控件画图：
public void run() { List<GpsSatellite> list=null; Canvas c = null; try { c = surfaceHolder.lockCanvas(null);
//设置画布背景色为白色，即自定义控件显示的背景色为白色：
c.drawRGB(255,255,255);
//初始化画板的中心坐标 cx = c.getWidth() / 2; cy = c.getWidth() / 2; synchronized (surfaceHolder) { doDraw(c,null); } } finally { if (c != null) { surfaceHolder.unlockCanvasAndPost(c); } } while (isRunning) { try{ list = queue.take(); } catch (InterruptedException e) { e.printStackTrace(); } try { c = surfaceHolder.lockCanvas(null); synchronized (surfaceHolder) { doDraw(c,list); } } finally { if (c != null) { surfaceHolder.unlockCanvasAndPost(c); } } } }
private void doDraw(Canvas canvas, List<GpsSatellite> satellites) { if (canvas != null) { // 绘制背景罗盘 drawBackground(canvas, cx, cy, compassRadius); //绘制卫星分布 if (satellites != null) { for (GpsSatellite satellite : satellites) { drawSatellite(canvas,satellite, cx, cy, compassRadius); } } } }
结果设置的画布的颜色失效，自定义控件背景显示为黑色：
正确修改绘图java文件：
*****************************************************************************************************************************************************************************************public void run() { List<GpsSatellite> list=null; Canvas c = null; try { c = surfaceHolder.lockCanvas(null);
//设置画布背景色为白色，即自定义控件显示的背景色为白色：
// c.drawRGB(255,255,255);
//此处设置画布颜色不行，得到doDraw()设置
//初始化画板的中心坐标 cx = c.getWidth() / 2; cy = c.getWidth() / 2; synchronized (surfaceHolder) { doDraw(c,null); } } finally { if (c != null) { surfaceHolder.unlockCanvasAndPost(c); } } while (isRunning) { try{ list = queue.take(); } catch (InterruptedException e) { e.printStackTrace(); } try { c = surfaceHolder.lockCanvas(null); synchronized (surfaceHolder) { doDraw(c,list); } } finally { if (c != null) { surfaceHolder.unlockCanvasAndPost(c); } } } }
private void doDraw(Canvas canvas, List<GpsSatellite> satellites) { if (canvas != null) {
canvas.drawRGB(255,255,255); // 绘制背景罗盘 drawBackground(canvas, cx, cy, compassRadius); //绘制卫星分布 if (satellites != null) { for (GpsSatellite satellite : satellites) { drawSatellite(canvas,satellite, cx, cy, compassRadius); } } } }
经过上述修改，画布显示为其设置的颜色。
综上所述，画布背景色的设置，应该在doDraw（）函数中设置，而不能直接在run()初始化时设置。
