Android 如何在XML定义的视图中使用画布绘制函数

我不想创建一个新的视图对象，我已经在XML中定义了一个简单的视图，我只想在它上面画一些条

在XML中，我有一个空白的LinearLayout，其中包含：

<View
    android:id="@+id/bars"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/grey" />

当我尝试设置颜色时，得到的错误是NullPointerException。如果我去掉那条线，当我试着画圆圈时，我会得到一个错误。我怎么能做我想做的

编辑-错误日志（我取出了setColor）：

05-19 00:56:14.100: E/AndroidRuntime(2422): FATAL EXCEPTION: main
05-19 00:56:14.100: E/AndroidRuntime(2422): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.aheadstudios.talkalytics/com.aheadstudios.talkalytics.ViewStatsPrototype}: java.lang.NullPointerException
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2308)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread.access$600(ActivityThread.java:153)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.os.Looper.loop(Looper.java:137)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread.main(ActivityThread.java:5227)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at java.lang.reflect.Method.invokeNative(Native Method)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at java.lang.reflect.Method.invoke(Method.java:511)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at dalvik.system.NativeStart.main(Native Method)
05-19 00:56:14.100: E/AndroidRuntime(2422): Caused by: java.lang.NullPointerException
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.graphics.Canvas.drawCircle(Canvas.java:961)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.aheadstudios.talkalytics.MultiStatsData.commonSetup(MultiStatsData.java:68)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.aheadstudios.talkalytics.MultiStatsData.<init>(MultiStatsData.java:50)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.aheadstudios.talkalytics.ViewStatsPrototype.setupMultiStatsData(ViewStatsPrototype.java:48)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.aheadstudios.talkalytics.ViewStatsPrototype.onCreate(ViewStatsPrototype.java:43)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.Activity.performCreate(Activity.java:5104)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2262)
05-19 00:56:14.100: E/AndroidRuntime(2422):     ... 11 more

05-19 00:56:14.100:E/AndroidRuntime（2422）：致命异常：主
05-19 00:56:14.100:E/AndroidRuntime（2422）：java.lang.RuntimeException:无法启动活动组件信息{com.aheadstudios.talkalytics/com.aheadstudios.talkalytics.ViewStatsPrototype}:java.lang.NullPointerException
05-19 00:56:14.100:E/AndroidRuntime（2422）：在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2308）
05-19 00:56:14.100:E/AndroidRuntime（2422）：在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2358）
05-19 00:56:14.100:E/AndroidRuntime（2422）：在android.app.ActivityThread.access$600（ActivityThread.java:153）
05-19 00:56:14.100:E/AndroidRuntime（2422）：在android.app.ActivityThread$H.handleMessage（ActivityThread.java:1247）
05-19 00:56:14.100:E/AndroidRuntime（2422）：在android.os.Handler.dispatchMessage（Handler.java:99）上
05-19 00:56:14.100:E/AndroidRuntime（2422）：在android.os.Looper.loop（Looper.java:137）上
05-19 00:56:14.100:E/AndroidRuntime（2422）：位于android.app.ActivityThread.main（ActivityThread.java:5227）
05-19 00:56:14.100:E/AndroidRuntime（2422）：位于java.lang.reflect.Method.Invokenactive（本机方法）
05-19 00:56:14.100:E/AndroidRuntime（2422）：位于java.lang.reflect.Method.invoke（Method.java:511）
05-19 00:56:14.100:E/AndroidRuntime（2422）：在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:795）
05-19 00:56:14.100:E/AndroidRuntime（2422）：位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:562）
05-19 00:56:14.100:E/AndroidRuntime（2422）：在dalvik.system.NativeStart.main（本机方法）
05-19 00:56:14.100:E/AndroidRuntime（2422）：由以下原因引起：java.lang.NullPointerException
05-19 00:56:14.100:E/AndroidRuntime（2422）：在android.graphics.Canvas.drawCircle（Canvas.java:961）上
05-19 00:56:14.100:E/AndroidRuntime（2422）：在com.aheadstudios.talkalytics.MultiStatsData.commonSetup（MultiStatsData.java:68）
05-19 00:56:14.100:E/AndroidRuntime（2422）：在com.aheadstudios.talkalytics.MultiStatsData。（MultiStatsData.java:50）
05-19 00:56:14.100:E/AndroidRuntime（2422）：在com.aheadstudios.talkalytics.ViewStatsPrototype.setupMultiStatsData（ViewStatsPrototype.java:48）
05-19 00:56:14.100:E/AndroidRuntime（2422）：位于com.aheadstudios.talkalytics.ViewStatsPrototype.onCreate（ViewStatsPrototype.java:43）
05-19 00:56:14.100:E/AndroidRuntime（2422）：在android.app.Activity.performCreate（Activity.java:5104）上
05-19 00:56:14.100:E/AndroidRuntime（2422）：在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1080）上
05-19 00:56:14.100:E/AndroidRuntime（2422）：在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2262）
05-19 00:56:14.100:E/AndroidRuntime（2422）：。。。还有11个

mPaint=new Paint（）

然后，代替条形图。绘制（c）

加

---

钢筋.立根拉深（新拉深（b））

@Sree但是我需要所有的画布绘制功能，绘制功能似乎只给你一个基本的形状？我要画里面有单词的条形图。好的，看，你初始化了

mPaint

对象了吗？我想它的初始化可能有问题。我放弃了，我只是要创建一个新的自定义视图对象，以便覆盖onDraw。

05-19 00:56:14.100: E/AndroidRuntime(2422): FATAL EXCEPTION: main
05-19 00:56:14.100: E/AndroidRuntime(2422): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.aheadstudios.talkalytics/com.aheadstudios.talkalytics.ViewStatsPrototype}: java.lang.NullPointerException
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2308)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread.access$600(ActivityThread.java:153)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.os.Looper.loop(Looper.java:137)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread.main(ActivityThread.java:5227)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at java.lang.reflect.Method.invokeNative(Native Method)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at java.lang.reflect.Method.invoke(Method.java:511)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at dalvik.system.NativeStart.main(Native Method)
05-19 00:56:14.100: E/AndroidRuntime(2422): Caused by: java.lang.NullPointerException
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.graphics.Canvas.drawCircle(Canvas.java:961)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.aheadstudios.talkalytics.MultiStatsData.commonSetup(MultiStatsData.java:68)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.aheadstudios.talkalytics.MultiStatsData.<init>(MultiStatsData.java:50)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.aheadstudios.talkalytics.ViewStatsPrototype.setupMultiStatsData(ViewStatsPrototype.java:48)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at com.aheadstudios.talkalytics.ViewStatsPrototype.onCreate(ViewStatsPrototype.java:43)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.Activity.performCreate(Activity.java:5104)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-19 00:56:14.100: E/AndroidRuntime(2422):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2262)
05-19 00:56:14.100: E/AndroidRuntime(2422):     ... 11 more