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;
}
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);
}
这里是一种方法来获得一个InputStream的文件在资产文件夹没有上下文，活动，片段或应用程序。如何从InputStream中获取数据取决于您。在这里的其他答案中有很多关于这个问题的建议。
科特林
val inputStream = ClassLoader::class.java.classLoader?.getResourceAsStream("assets/your_file.ext")
Java
InputStream inputStream = ClassLoader.class.getClassLoader().getResourceAsStream("assets/your_file.ext");
如果正在使用自定义ClassLoader，那么所有的赌注都是无效的。
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
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()。
