create a cache file adapter

This makes the main parts of the JSONLayoutAdapter generic so
that other adapters who would like to use a cache copy of some
remote url may do so

1 files changed, 143 insertions, 0 deletions

diff --git a/src/org/linaro/connect/CachedJSONLayoutAdapter.java b/src/org/linaro/connect/CachedJSONLayoutAdapter.java
new file mode 100644
index 0000000..4c40291
--- /dev/null
+++ b/src/org/linaro/connect/CachedJSONLayoutAdapter.java
@@ -0,0 +1,143 @@
+package org.linaro.connect;
+
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.InputStream;
+
+import org.json.JSONObject;
+
+import android.content.Context;
+import android.os.AsyncTask;
+import android.util.Log;
+import android.widget.ArrayAdapter;
+
+public abstract class CachedJSONLayoutAdapter extends ArrayAdapter<JSONItem> {
+
+	private long mLastCheck = 0;
+	private long mInterval = 0;
+	private int mCacheResId = 0;
+	private String mCacheFile;
+	private String mJSONUrl;
+
+	public CachedJSONLayoutAdapter(Context ctx, int resId, int textViewResId) {
+		super(ctx, resId, textViewResId);
+	}
+
+	protected abstract void updateLayout(JSONObject jso);
+
+	protected void setRefreshInterval(long interval) {
+		mInterval = interval;
+	}
+
+	/**
+	 * This can be used to tell the adapter we have a default version of the
+	 * file that shipped with the app.
+	 */
+	protected void setCacheResourceId(int id) {
+		mCacheResId = id;
+	}
+
+	/**
+	 * Sets the filename that is used to read/write the cache to
+	 */
+	protected void setCacheFileName(String file) {
+		mCacheFile = file;
+	}
+
+	protected void setJSONUrl(String url) {
+		mJSONUrl = url;
+	}
+
+	void refresh() {
+		JSONObject jso = getJSONObject();
+		updateLayout(jso);
+
+		long now = System.currentTimeMillis();
+		if( now > mLastCheck + mInterval) {
+			new DownloadJSONTask().execute(mJSONUrl);
+			mLastCheck = now;
+		}
+	}
+
+	//this shouldn't run when writeCacheFile is run
+	private synchronized InputStream getJSONInputStream() {
+		InputStream is = null;
+		try {
+			is = getContext().openFileInput(mCacheFile);
+			Log.v(LinaroConnect.TAG, "cache file found: " + mCacheFile);
+		} catch (FileNotFoundException e) {
+			if (mCacheResId > 0 )
+				is = getContext().getResources().openRawResource(mCacheResId);
+		}
+		return is;
+	}
+
+	private JSONObject getJSONObject() {
+		InputStream is = getJSONInputStream();
+		if (is == null)
+			return null;
+		return JSONUtils.getObject(is);
+	}
+
+	//this shouldn't run when getJSONInputStream is run
+	private synchronized void writeCacheFile(Context ctx, String json) {
+		FileOutputStream os = null;
+		try {
+			os = ctx.openFileOutput(mCacheFile, 0);
+		}
+		catch(Exception e) {
+			Log.e(LinaroConnect.TAG, "Error opening cache for writing", e);
+			return;
+		}
+
+		try {
+			os.write(json.getBytes());
+		}
+		catch(Exception e) {
+			Log.e(LinaroConnect.TAG, "Error writing cache", e);
+			return;
+		}
+
+		try {
+			os.close();
+		}
+		catch(Exception e) {}
+	}
+
+	/**
+	 * checks to see if there's a new JSON file on the server
+	 */
+	private class DownloadJSONTask extends AsyncTask<String, Void, Boolean> {
+		@Override
+		protected Boolean doInBackground(String... urls) {
+			String jsonNew = null;
+			boolean layoutChanged = false;
+			try {
+				InputStream is = LinaroConnect.getUrlInputStream(urls[0], false);
+				jsonNew = JSONUtils.toString(is);
+
+			} catch (Exception e) {
+				Log.e(LinaroConnect.TAG, "Error dowloading for cache: " + urls[0], e);
+			}
+
+			InputStream is = getJSONInputStream();
+			String jsonOrig = JSONUtils.toString(is);
+
+			layoutChanged = ( jsonNew != null && !jsonNew.equals(jsonOrig) );
+			if( layoutChanged) {
+				Log.i(LinaroConnect.TAG, "cache update found");
+				writeCacheFile(getContext(), jsonNew);
+			}
+
+			return new Boolean(layoutChanged);
+		}
+
+		@Override
+		protected void onPostExecute(Boolean result) {
+			if( result.booleanValue() ) {
+				JSONObject jso = getJSONObject();
+				updateLayout(jso);
+			}
+		}
+	}
+}