亲爱的Stackoverflowers,
我目前正在从我的原始资源中解析一个大的json文件.我不得不逐行更改读取使用Reader对象和gson,以逃避内存不足异常.到现在为止还挺好.
现在这一切都发生在异步任务中,我希望通过使用publishProgress()让用户通知某种加载屏幕的进度.
InputStream raw = getResources().openRawResource(R.raw.json); Reader rd = new BufferedReader(new InputStreamReader(raw)); Gson gson = new Gson(); mReadobjects = gson.fromJson(rd,ReadobjectList.class);
这是我现在正在阅读文件的方式,但我不知道是否(以及如何)我可以从GSON或Reader对象获得任何类型的进度更新.
任何帮助是极大的赞赏！
解决方法
您必须围绕InputStream(或Reader)编写包装器.
像这样的东西应该工作：
public class ProgressInputStream extends FilterInputStream {
private final int size;
private long bytesRead;
private int percent;
private List<Listener> listeners = new ArrayList<>();
public ProgressInputStream(InputStream in) {
super(in);
try {
size = available();
if (size == 0) throw new IOException();
} catch (IOException e) {
throw new RuntimeException("This reader can only be used on InputStreams with a kNown size",e);
}
bytesRead = 0;
percent = 0;
}
public void addListener(Listener listener) {
listeners.add(listener);
}
public void removeListener(Listener listener) {
listeners.remove(listener);
}
@Override
public int read() throws IOException {
int b = super.read();
updateProgress(1);
return b;
}
@Override
public int read(@NonNull byte[] b) throws IOException {
return updateProgress(super.read(b));
}
@Override
public int read(@NonNull byte[] b,int off,int len) throws IOException {
return updateProgress(super.read(b,off,len));
}
@Override
public long skip(long n) throws IOException {
return updateProgress(super.skip(n));
}
@Override
public void mark(int readLimit) {
throw new UnsupportedOperationException();
}
@Override
public void reset() throws IOException {
throw new UnsupportedOperationException();
}
@Override
public boolean markSupported() {
return false;
}
private <T extends Number> T updateProgress(T numBytesRead) {
if (numBytesRead.longValue() > 0) {
bytesRead += numBytesRead.longValue();
if (bytesRead * 100 / size > percent) {
percent = (int) (bytesRead * 100 / size);
for (Listener listener : listeners) {
listener.onProgressChanged(percent);
}
}
}
return numBytesRead;
}
public interface Listener {
void onProgressChanged(int percentage);
}
}
如何使用：
ProgressInputStream raw = new ProgressInputStream(getResources().openRawResource(R.raw.json));
raw.addListener(new ProgressInputStream.Listener() {
@Override
public void onProgressChanged(int percentage) {
publishProgress(percentage);
}
});
Reader rd = new BufferedReader(new InputStreamReader(raw));