将android.graphics.path值转换为字符串？

Question

我有一个ArrayList的路径值。我需要将其转换为字符串值并知道路径中所有坐标。 下面是我整理了一下代码：

private ArrayList<Path> pointsToDraw = new ArrayList<Path>(); 
private List<String> stringPoints ; 



synchronized(pointsToDraw){ 
        for(Path path : pointsToDraw) 
        { 
         stringPoints.add(String.valueOf(path)); 
        } 

        TextView b1Text = (TextView) findViewById(R.id.GText); 
        for(String s : stringPoints) 
        { 
         b1Text.setText(s); 
        } 
        } 

我在运行时得到一个异常。以下是日志内容：

02-21 18:18:29.323: E/AndroidRuntime(512): FATAL EXCEPTION: main 
02-21 18:18:29.323: E/AndroidRuntime(512): java.lang.NullPointerException 
02-21 18:18:29.323: E/AndroidRuntime(512): at learn.myandroidapp.hr.HRCanvas$1.onClick(HRCanvas.java:78) 
02-21 18:18:29.323: E/AndroidRuntime(512): at android.view.View.performClick(View.java:3511) 
02-21 18:18:29.323: E/AndroidRuntime(512): at android.view.View$PerformClick.run(View.java:14105) 
02-21 18:18:29.323: E/AndroidRuntime(512): at android.os.Handler.handleCallback(Handler.java:605) 
02-21 18:18:29.323: E/AndroidRuntime(512): at android.os.Handler.dispatchMessage(Handler.java:92) 
02-21 18:18:29.323: E/AndroidRuntime(512): at android.os.Looper.loop(Looper.java:137) 
02-21 18:18:29.323: E/AndroidRuntime(512): at android.app.ActivityThread.main(ActivityThread.java:4424) 
02-21 18:18:29.323: E/AndroidRuntime(512): at java.lang.reflect.Method.invokeNative(Native Method) 
02-21 18:18:29.323: E/AndroidRuntime(512): at java.lang.reflect.Method.invoke(Method.java:511) 
02-21 18:18:29.323: E/AndroidRuntime(512): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
02-21 18:18:29.323: E/AndroidRuntime(512): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
02-21 18:18:29.323: E/AndroidRuntime(512): at dalvik.system.NativeStart.main(Native Method) 

我在哪里出错了？请帮忙！

Answer 1

stringPoints尚未分配清单。

变化：

private List<String> stringPoints ; 

到：

private List<String> stringPoints = new ArrayList<String>();