如何从 Android Studio 中的资产中读取文本文件？答案

【问题标题】：How to read a text file from assets in Android Studio?如何从 Android Studio 中的资产中读取文本文件？
【发布时间】：2016-06-30 10:54:47
【问题描述】：

我在 Android Studio 的资产文件目录中可能有 wifi2.txt 文件。但是，当我尝试访问它时，我不断收到 NULLPointException。我的代码如下：（提前非常感谢）

             //CSV FILE READING
    File file = null;



    try {



        FileInputStream is = new FileInputStream(file);

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(getAssets().open("wifi2.txt")));
            String line;
            Log.e("Reader Stuff",reader.readLine());
            while ((line = reader.readLine()) != null) {
                Log.e("code",line);
                String[] RowData = line.split(",");
                LatLng centerXY = new LatLng(Double.valueOf(RowData[1]), Double.valueOf(RowData[2]));
                if (RowData.length == 4) {
                    mMap.addMarker(new MarkerOptions().position(centerXY).title(String.valueOf(RowData[0]) + String.valueOf(RowData[3])).icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN)));
                }

            }

        } catch (IOException ex) {
           ex.printStackTrace();
        } finally {
            try {
                is.close();
            } catch (IOException e) {
               e.printStackTrace();
            }
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }


   //Done with CSV File Reading

【问题讨论】：

调用new FileInputStream(null) 显然会导致NPE ...
What is a NullPointerException, and how do I fix it?的可能重复

标签： android android-studio nullpointerexception android-assets

【解决方案1】：

在 Kotlin 中，我们可以做到这一点：-

val string = requireContext().assets.open("wifi2.txt").bufferedReader().use {
                it.readText()
            }

【讨论】：

结果如何？

【解决方案2】：

File file = null;
try {
    FileInputStream is = new FileInputStream(file);

实际上，您并没有在任何地方使用 FileInputStream。就用这段代码

  try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(getAssets().open("wifi2.txt")));
        String line;
        Log.e("Reader Stuff",reader.readLine());
        while ((line = reader.readLine()) != null) {
            Log.e("code",line);
            String[] RowData = line.split(",");
            LatLng centerXY = new LatLng(Double.valueOf(RowData[1]), Double.valueOf(RowData[2]));
            if (RowData.length == 4) {
                mMap.addMarker(new MarkerOptions().position(centerXY).title(String.valueOf(RowData[0]) + String.valueOf(RowData[3])).icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN)));
            }

        }

    } catch (IOException ex) {
       ex.printStackTrace();
    }

【讨论】：

【解决方案3】：

从assets读取文件的方法：

    public static String readFile(AssetManager mgr, String path) {
        String contents = "";
        InputStream is = null;
        BufferedReader reader = null;
        try {
            is = mgr.open(path);
            reader = new BufferedReader(new InputStreamReader(is));
            contents = reader.readLine();
            String line = null;
            while ((line = reader.readLine()) != null) {
                contents += '\n' + line;
            }
        } catch (final Exception e) {
            e.printStackTrace();
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException ignored) {
                }
            }
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException ignored) {
                }
            }
        }
        return contents;
    }

【讨论】：

【解决方案4】：

用法： String yourData = LoadData("wifi2.txt");

假设 wifi2.txt 位于assets

 public String LoadData(String inFile) {
        String tContents = "";

    try {
        InputStream stream = getAssets().open(inFile);

        int size = stream.available();
        byte[] buffer = new byte[size];
        stream.read(buffer);
        stream.close();
        tContents = new String(buffer);
    } catch (IOException e) {
        // Handle exceptions here
    }

    return tContents;

 }

Reference

【讨论】：

【解决方案5】：

我使用 kotlin 从资产文件加载文本的解决方案

object AssetsLoader {

    fun loadTextFromAsset(context: Context, file: String): String {
        return context.assets.open(file).bufferedReader().use { reader ->
            reader.readText()
        }
    }

}

像这样使用它：

val text = AssetsLoader.loadTextFromAsset(context, "test.json")

【讨论】：