android 画布异常，帮忙看一下是哪里的问题

想在画布上面画折线图，然后系统把这一句报错： canvas.drawText(Title, 150, 50, paint);错误信息：
10-20 03:04:22.811: I/dalvikvm(1254): threadid=3: reacting to signal 3
10-20 03:04:22.852: I/dalvikvm(1254): Wrote stack traces to '/data/anr/traces.txt'
10-20 03:04:23.202: D/gralloc_goldfish(1254): Emulator without GPU emulation detected.
10-20 03:04:23.232: I/System.out(1254): 111111
10-20 03:04:23.262: D/AndroidRuntime(1254): Shutting down VM
10-20 03:04:23.262: W/dalvikvm(1254): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
10-20 03:04:23.291: E/AndroidRuntime(1254): FATAL EXCEPTION: main
10-20 03:04:23.291: E/AndroidRuntime(1254): java.lang.NullPointerException
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.graphics.Canvas.drawText(Canvas.java:1368)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at com.example.zhexiantu.ChartView.onDraw(ChartView.java:85)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.View.draw(View.java:10978)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.ViewGroup.drawChild(ViewGroup.java:2887)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2489)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.View.draw(View.java:10981)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.widget.FrameLayout.draw(FrameLayout.java:450)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.ViewGroup.drawChild(ViewGroup.java:2887)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2489)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.ViewGroup.drawChild(ViewGroup.java:2885)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2489)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.View.draw(View.java:10981)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.widget.FrameLayout.draw(FrameLayout.java:450)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:2126)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.ViewRootImpl.draw(ViewRootImpl.java:2026)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1634)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.os.Looper.loop(Looper.java:137)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at android.app.ActivityThread.main(ActivityThread.java:4424)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at java.lang.reflect.Method.invokeNative(Native Method)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at java.lang.reflect.Method.invoke(Method.java:511)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
10-20 03:04:23.291: E/AndroidRuntime(1254):  at dalvik.system.NativeStart.main(Native Method)
10-20 03:04:23.331: I/dalvikvm(1254): threadid=3: reacting to signal 3
10-20 03:04:23.361: I/dalvikvm(1254): Wrote stack traces to '/data/anr/traces.txt'
10-20 03:04:24.011: I/dalvikvm(1254): threadid=3: reacting to signal 3
10-20 03:04:24.031: I/dalvikvm(1254): Wrote stack traces to '/data/anr/traces.txt'
10-20 03:04:24.081: I/dalvikvm(1254): threadid=3: reacting to signal 3
10-20 03:04:24.091: I/dalvikvm(1254): Wrote stack traces to '/data/anr/traces.txt'
10-20 03:04:32.111: I/Process(1254): Sending signal. PID: 1254 SIG: 9
10-20 03:07:11.221: I/dalvikvm(1326): threadid=3: reacting to signal 3
10-20 03:07:11.281: I/dalvikvm(1326): Wrote stack traces to '/data/anr/traces.txt'
10-20 03:07:11.572: D/gralloc_goldfish(1326): Emulator without GPU emulation detected.
10-20 03:07:11.621: I/System.out(1326): 111111
10-20 03:07:11.621: D/AndroidRuntime(1326): Shutting down VM
10-20 03:07:11.621: W/dalvikvm(1326): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
10-20 03:07:11.641: E/AndroidRuntime(1326): FATAL EXCEPTION: main
10-20 03:07:11.641: E/AndroidRuntime(1326): java.lang.NullPointerException
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.graphics.Canvas.drawText(Canvas.java:1368)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at com.example.zhexiantu.ChartView.onDraw(ChartView.java:85)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.View.draw(View.java:10978)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.ViewGroup.drawChild(ViewGroup.java:2887)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2489)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.View.draw(View.java:10981)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.widget.FrameLayout.draw(FrameLayout.java:450)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.ViewGroup.drawChild(ViewGroup.java:2887)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2489)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.ViewGroup.drawChild(ViewGroup.java:2885)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2489)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.View.draw(View.java:10981)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.widget.FrameLayout.draw(FrameLayout.java:450)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:2126)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.ViewRootImpl.draw(ViewRootImpl.java:2026)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1634)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.os.Looper.loop(Looper.java:137)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at android.app.ActivityThread.main(ActivityThread.java:4424)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at java.lang.reflect.Method.invokeNative(Native Method)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at java.lang.reflect.Method.invoke(Method.java:511)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
10-20 03:07:11.641: E/AndroidRuntime(1326):  at dalvik.system.NativeStart.main(Native Method)
10-20 03:07:11.742: I/dalvikvm(1326): threadid=3: reacting to signal 3
10-20 03:07:11.751: I/dalvikvm(1326): Wrote stack traces to '/data/anr/traces.txt'
10-20 03:07:12.262: I/dalvikvm(1326): threadid=3: reacting to signal 3
10-20 03:07:12.272: I/dalvikvm(1326): Wrote stack traces to '/data/anr/traces.txt'
10-20 03:07:13.702: I/Process(1326): Sending signal. PID: 1326 SIG: 9
android异常