方案如下:
我有一个活动RunTrainingWorkoutsView,它使用XML布局_run_workout.xml_,其中一些标签由CountDownTimer更新.工作正常…
现在,除了每秒通过onTick()CountDownTimer对象的回调方法更新的标签,我想在我的_run_workout.xml layout_中添加一个自定义表面视图,它将绘制一些每秒由同一onTick()方法更新的弧. .
我的run_workout.xml:
android:id="@+id/counter_clock_surface"
android:layout_width="300dp"
android:layout_height="240dp">
我的自定义View扩展了surfaceView
public class CounterClockView extends SurfaceView {
Paint paint = new Paint();
Paint paint2 = new Paint();
final RectF rect = new RectF();
final RectF rect2 = new RectF();
int counterArcAngle = 15;
//constructor
public CounterClockView(Context context, AttributeSet attributeSet) {
super(context);
//setting some paint properties...
this.setBackgroundColor(Color.TRANSPARENT);
}
@Override
public void onDraw(Canvas canvas) {
rect.set(50, 50, 150, 150);
rect2.set(50, 50, 150, 150);
this.layout(0, 0, 200, 200);
canvas.drawArc(rect, -90, 360, false, paint);
canvas.drawArc(rect2, -90, counterArcAngle, false, paint2);
}
扩展活动的主要类是使用以下代码在布局中获取对自定义surfaceView的引用:
//counterClockView is declared outside of onCreate() as CounterClockView counterClockView;
//later in onCreate(){....
counterClockView = (CounterClockView) findViewById(R.id.counter_clock_surface);
问题是改变customView对象的成员变量的值(counterClockView)
counterClockView.counterArcAngle = 10;
将崩溃应用程序…
另外,从我的主要活动开始,我想调用invalidate()方法在更改counterArcAngle值后重做表面视图,但这会导致应用程序崩溃…
为什么不能创建counterClockView对象并将其引用到相同类型的xml布局元素并更改其外观,使其无效等?
编辑LogCat:
threadid=1: thread exiting with uncaught exception (group=0x40015560)
ERROR/AndroidRuntime(487): FATAL EXCEPTION: main
ERROR/AndroidRuntime(487): java.lang.RuntimeException: Unable to start activity ComponentInfo{training.timer/training.timer.RunTrainingWorkoutsView}: java.lang.NullPointerException
ERROR/AndroidRuntime(487): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
ERROR/AndroidRuntime(487): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
ERROR/AndroidRuntime(487): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
ERROR/AndroidRuntime(487): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
ERROR/AndroidRuntime(487): at android.os.Handler.dispatchMessage(Handler.java:99)
ERROR/AndroidRuntime(487): at android.os.Looper.loop(Looper.java:123)
ERROR/AndroidRuntime(487): at android.app.ActivityThread.main(ActivityThread.java:3683)
ERROR/AndroidRuntime(487): at java.lang.reflect.Method.invokeNative(Native Method)
ERROR/AndroidRuntime(487): at java.lang.reflect.Method.invoke(Method.java:507)
ERROR/AndroidRuntime(487): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
ERROR/AndroidRuntime(487): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
ERROR/AndroidRuntime(487): at dalvik.system.NativeStart.main(Native Method)
ERROR/AndroidRuntime(487): Caused by: java.lang.NullPointerException
ERROR/AndroidRuntime(487): at training.timer.RunTrainingWorkoutsView.onCreate(RunTrainingWorkoutsView.java:72)
ERROR/AndroidRuntime(487): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
ERROR/AndroidRuntime(487): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
ERROR/AndroidRuntime(487): ... 11 more
解决方法:
经过3天的攻击,我的头靠在墙上,谷歌搜索,stacOverflowing等我得到了它.
实际上,这是一个愚蠢的小事……
我的XML文件,我定义了包含一些常见的android视图(即textView和按钮)的布局和我的自定义视图CounterClockView:
android:id="@+id/counter_clock_surface"
android:layout_width="300dp"
android:layout_height="240dp">
我必须增加一条线!
xmlns:android="/apk/res/android" !!!
android:id="@+id/counter_clock_surface"
android:layout_width="300dp"
android:layout_height="240dp">
我不知道为什么这个命名空间行产生了如此巨大的差异,但它的效果很好!
现在,我可以在CountDownTimer()的每个onTick()上从我的主要活动更新我的自定义视图…
标签:android,android-layout,surfaceview
来源: https://codeday.me/bug/1003/1846023.html