java.lang.NullPointerException: lock == null 来自 InputStreamReader

Question

So I'm trying to parse an.obj wavefront file to be displayed with OpenGL ES, thing is, I'm getting the Nullpointer as if the file did not exist or was empty (?). I tried two different ways of getting to parse the file, also made sure there were no empty lines on it, put it in different folders (assets, src root, res, etc...) but the result is the same. Maybe the error I'm getting is more to do with the OpenGL part of the code? But I'm kinda lost, because apparently it should work... Also tried buffering the file outside the function, same happened. From another question here, the problem the person had, had to do with " trying to update UI from worker Thread ". Async did not help me here.

I got the code idea form this blog: http://etcodehome.blogspot.com/2011/07/android-rendering-3d-blender-models.html

And the file to base my work on from here: https://github.com/MartianIsMe/earth-live-wallpaper/blob/d71902aa642bad0c10fc46d6839ced6e15995f7b/%20earth-live-wallpaper/SLWP/src/com/seb/SLWP/DeathStar.java

 fun loadObjFile() {
    try {
        var str: String
        var tmp: Array<String>
        var ftmp: Array<String>
        var v: Float
        val vlist = ArrayList<Float>()
        val nlist = ArrayList<Float>()
        val fplist = ArrayList<Fp>()
        val mContext: Context? = null
        //val inb: BufferedReader = File("androidmodel.obj").bufferedReader()
        //val inputString = inb.use { it.readText() }
        val inb = BufferedReader(InputStreamReader(mContext?.getAssets()?.open
        ("src/main/res/androidmodel.obj")), 1024) //Error is here at com.example.xxx.MyGLRenderer.loadObjFile

        while (inb.readLine().also { str = it } != null) {
            tmp = str.split(" ".toRegex()).toTypedArray()
            //Parse the vertices
            if (tmp[0].equals("v", ignoreCase = true)) {
                for (i in 1..3) {
                    v = tmp[i].toFloat()
                    vlist.add(v)
                }
            }
            //Parse the vertex normals
            if (tmp[0].equals("vn", ignoreCase = true)) {
                for (i in 1..3) {
                    v = tmp[i].toFloat()
                    nlist.add(v)
                }
            }
            //Parse the faces/indices
            if (tmp[0].equals("f", ignoreCase = true)) {
                for (i in 1..3) {
                    ftmp = tmp[i].split("/".toRegex()).toTypedArray()
                    val chi = ftmp[0].toInt() - 1.toLong()
                    var cht = 0
                    if (ftmp[1] != "") cht = ftmp[1].toInt() - 1
                    val chn = ftmp[2].toInt() - 1
                    fplist.add(Fp(chi, cht, chn))
                }
                NBFACES++
            }
        }
        val vbb = ByteBuffer.allocateDirect(fplist.size * 4 * 3)
        vbb.order(ByteOrder.nativeOrder())
        mVertexBuffer = vbb.asFloatBuffer()
        val nbb = ByteBuffer.allocateDirect(fplist.size * 4 * 3)
        nbb.order(ByteOrder.nativeOrder())
        mNormBuffer = nbb.asFloatBuffer()
        for (j in fplist.indices) {
            mVertexBuffer?.put(vlist[(fplist[j].Vi * 3).toInt()])
            mVertexBuffer?.put(vlist[(fplist[j].Vi * 3 + 1).toInt()])
            mVertexBuffer?.put(vlist[(fplist[j].Vi * 3 + 2).toInt()])
            mNormBuffer?.put(nlist[fplist[j].Ni * 3])
            mNormBuffer?.put(nlist[fplist[j].Ni * 3 + 1])
            mNormBuffer?.put(nlist[fplist[j].Ni * 3 + 2])
        }
        mIndexBuffer = CharBuffer.allocate(fplist.size)
        for (j in fplist.indices) {
            mIndexBuffer?.put(j.toChar())
        }
        mVertexBuffer?.position(0)
        mNormBuffer?.position(0)
        mIndexBuffer?.position(0)
    } catch (e: IOException) {
        e.printStackTrace()
    }
}

private class Fp
(var Vi: Long, var Ti: Int, var Ni: Int)

Answer 1

The problem is that you pass null into InputStreamReader . The path to the asset is wrong.

• First of all the file should be located under assets directory that is positioned on the same level in directory hierarchy as the java and res folder.
• Second, you should pass path relative to the assets directory. So if your file is located directly under assets then the relative path is "androidmodel.obj" . Thus, creating input stream will look like this:

InputStreamReader(mContext?.getAssets()?.open("androidmodel.obj"))

But I strongly recommend you to check for non-null because if mContext is null - the issue will return.

mContext?.getAssets()?.open("androidmodel.obj")?.let { nonNullAsset ->
    InputStreamReader(nonNullAsset)
}

This part is crucial ?.let { as it runs the let function only if the object is not null.

If there is no assets directory, just create it as a simple directory and it will be picked up by IDE automatically:

Update

As the NPE still occurs the only reason left is the null value in mContext variable. Make sure it is initialized.

And after a little bit more digging, I can say that this was the issue from the beginning. Any attempt to pass the wrong path of a file to the assets.open(fileName) function will result in FileNotFoundException . Thus, even though the path you use is wrong you did not even reach the point of opening a file as the context is null.