public class Utils {
    public static List<Message> getMessages() {
        //File file = new File("file:///android_asset/helloworld.txt");
        AssetManager assetManager = getAssets();
        InputStream ims = assetManager.open("helloworld.txt");    
     }
}

我正在使用这段代码试图从资产读取文件。我尝试了两种方法。首先,当使用文件时,我收到FileNotFoundException,当使用资产管理器getAssets()方法不被识别。 有什么解决办法吗?


当前回答

在MainActivity.java

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView tvView = (TextView) findViewById(R.id.tvView);

        AssetsReader assetsReader = new AssetsReader(this);
        if(assetsReader.getTxtFile(your_file_title)) != null)
        {
            tvView.setText(assetsReader.getTxtFile(your_file_title)));
        }
    }

此外,您还可以创建单独的类来完成所有工作

public class AssetsReader implements Readable{

    private static final String TAG = "AssetsReader";


    private AssetManager mAssetManager;
    private Activity mActivity;

    public AssetsReader(Activity activity) {
        this.mActivity = activity;
        mAssetManager = mActivity.getAssets();
    }

    @Override
    public String getTxtFile(String fileName)
    {
        BufferedReader reader = null;
        InputStream inputStream = null;
        StringBuilder builder = new StringBuilder();

        try{
            inputStream = mAssetManager.open(fileName);
            reader = new BufferedReader(new InputStreamReader(inputStream));

            String line;

            while((line = reader.readLine()) != null)
            {
                Log.i(TAG, line);
                builder.append(line);
                builder.append("\n");
            }
        } catch (IOException ioe){
            ioe.printStackTrace();
        } finally {

            if(inputStream != null)
            {
                try {
                    inputStream.close();
                } catch (IOException ioe){
                    ioe.printStackTrace();
                }
            }

            if(reader != null)
            {
                try {
                    reader.close();
                } catch (IOException ioe)
                {
                    ioe.printStackTrace();
                }
            }
        }
        Log.i(TAG, "builder.toString(): " + builder.toString());
        return builder.toString();
    }
}

在我看来,最好创建一个界面,但这不是必要的

public interface Readable {
    /**
     * Reads txt file from assets
     * @param fileName
     * @return string
     */
    String getTxtFile(String fileName);
}

其他回答

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;
}

如果你用的是Activity以外的类,你可能会想,

BufferedReader bufferedReader = new BufferedReader(new InputStreamReader( YourApplication.getInstance().getAssets().open("text.txt"), "UTF-8"));

Scanner类可以简化这一点。

        StringBuilder sb=new StringBuilder();
        Scanner scanner=null;
        try {
            scanner=new Scanner(getAssets().open("text.txt"));
            while(scanner.hasNextLine()){
                sb.append(scanner.nextLine());
                sb.append('\n');
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(scanner!=null){try{scanner.close();}catch (Exception e){}}
        }
        mTextView.setText(sb.toString());

kotlin的一行解决方案:

fun readFileText(fileName: String): String {
    return assets.open(fileName).bufferedReader().use { it.readText() }
}

此外,您可以使用它作为扩展函数无处不在

fun Context.readTextFromAsset(fileName : String) : String{
     return assets.open(fileName).bufferedReader().use { 
     it.readText()}
}

简单地调用任何上下文类

context.readTextFromAsset("my file name")
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()。