迟到总比不到好。

在某些情况下，我很难逐行阅读文件。 下面的方法是到目前为止我发现的最好的方法，我推荐它。

使用:字符串yourData = LoadData(“YourDataFile.txt”);

YourDataFile.txt假定驻留在资产/

 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;

 }

public String ReadFromfile(String fileName, Context context) {
    StringBuilder returnString = new StringBuilder();
    InputStream fIn = null;
    InputStreamReader isr = null;
    BufferedReader input = null;
    try {
        fIn = context.getResources().getAssets()
                .open(fileName, Context.MODE_WORLD_READABLE);
        isr = new InputStreamReader(fIn);
        input = new BufferedReader(isr);
        String line = "";
        while ((line = input.readLine()) != null) {
            returnString.append(line);
        }
    } catch (Exception e) {
        e.getMessage();
    } finally {
        try {
            if (isr != null)
                isr.close();
            if (fIn != null)
                fIn.close();
            if (input != null)
                input.close();
        } catch (Exception e2) {
            e2.getMessage();
        }
    }
    return returnString.toString();
}

您可以从文件中加载内容。考虑文件在资产文件夹中。

public static InputStream loadInputStreamFromAssetFile(Context context, String fileName){
    AssetManager am = context.getAssets();
    try {
        InputStream is = am.open(fileName);
        return is;
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

public static String loadContentFromFile(Context context, String path){
    String content = null;
    try {
        InputStream is = loadInputStreamFromAssetFile(context, path);
        int size = is.available();
        byte[] buffer = new byte[size];
        is.read(buffer);
        is.close();
        content = new String(buffer, "UTF-8");
    } catch (IOException ex) {
        ex.printStackTrace();
        return null;
    }
    return content;
}

现在可以通过调用函数来获取内容，如下所示

String json= FileUtil.loadContentFromFile(context, "data.json");

考虑到数据。json存储在Application\app\src\main\assets\data.json中

下面是一个在资产中读取文件的方法:

/**
 * Reads the text of an asset. Should not be run on the UI thread.
 * 
 * @param mgr
 *            The {@link AssetManager} obtained via {@link Context#getAssets()}
 * @param path
 *            The path to the asset.
 * @return The plain text of the asset
 */
public static String readAsset(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;
}

getAssets()

它只适用于其他任何类的活动，你必须为它使用上下文。

让Utils类的构造函数将活动引用(丑陋的方式)或应用程序上下文作为参数传递给它。在Utils类中使用getAsset()。

cityfile.txt

   public void getCityStateFromLocal() {
        AssetManager am = getAssets();
        InputStream inputStream = null;
        try {
            inputStream = am.open("city_state.txt");
        } catch (IOException e) {
            e.printStackTrace();
        }
        ObjectMapper mapper = new ObjectMapper();
        Map<String, String[]> map = new HashMap<String, String[]>();
        try {
            map = mapper.readValue(getStringFromInputStream(inputStream), new TypeReference<Map<String, String[]>>() {
            });
        } catch (IOException e) {
            e.printStackTrace();
        }
        ConstantValues.arrayListStateName.clear();
        ConstantValues.arrayListCityByState.clear();
        if (map.size() > 0)
        {
            for (Map.Entry<String, String[]> e : map.entrySet()) {
                CityByState cityByState = new CityByState();
                String key = e.getKey();
                String[] value = e.getValue();
                ArrayList<String> s = new ArrayList<String>(Arrays.asList(value));
                ConstantValues.arrayListStateName.add(key);
                s.add(0,"Select City");
                cityByState.addValue(s);
                ConstantValues.arrayListCityByState.add(cityByState);
            }
        }
        ConstantValues.arrayListStateName.add(0,"Select States");
    }
 // Convert InputStream to String
    public String getStringFromInputStream(InputStream is) {
        BufferedReader br = null;
        StringBuilder sb = new StringBuilder();
        String line;
        try {
            br = new BufferedReader(new InputStreamReader(is));
            while ((line = br.readLine()) != null) {
                sb.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (br != null) {
                try {
                    br.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

        return sb + "";

    }