修复部分bug

app/src/main/java/com/gh/common/view/DownloadDialog.java

@@ -57,15 +57,15 @@ public class DownloadDialog implements OnCollectionCallBackListener {
 
 	private boolean isShow;
 
-	private DownloadDialog(Context context) {
-		this.context = context;
+	private DownloadDialog() {
 		isShow = false;
 	}
 
 	public static DownloadDialog getInstance(Context context) {
 		if (instance == null) {
-			instance = new DownloadDialog(context);
+			instance = new DownloadDialog();
 		}
+		instance.context = context;
 		return instance;
 	}