问题
I'm using Picasso library for image downloading from the network. I just wonder whether I can use a progress dialog or a GIF image as a place holder? Also any idea on how to make place holder image to be smaller (and fit in centre) than the actual image that is downloaded?
I tried going thru the samples but no luck. Any one here who got this to work?
回答1:
You can use a placeholder image by using the *.placeholder(R.drawable.image_name)* in your Picasso call like:
Picasso.with(context)
.load(imageUrl)
.placeholder(R.drawable.image_name)
If you want to use a progress bar instead of a placeholder image you can create a callback inside the .into function. Do something similar to the following:
in your view:
//create the progressBar here and set it to GONE. This can be your adapters list item view for example
<RelativeLayout
android:id="@+id/myContainer"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<ProgressBar
android:id="@+id/progressBar"
style="?android:attr/progressBarStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:visibility="gone"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:layout_marginTop="20dp"
android:layout_marginBottom="20dp"/>
<ImageView
android:id="@+id/myImageView"
android:layout_width="60dp"
android:layout_height="60dp"
android:layout_gravity="center"
android:layout_margin="5dp"
android:paddingLeft="60dp"
android:scaleType="centerCrop"></ImageView>
</RelativeLayout>
In your adapter/class:
//create a new progress bar for each image to be loaded
ProgressBar progressBar = null;
if (view != null) {
progressBar = (ProgressBar) view.findViewById(R.id.progressBar);
progressBar.setVisibility(View.VISIBLE);
}
//get your image view
ImageView myImage = (ImageView) view.findViewById(R.id.myImageView);
//load the image url with a callback to a callback method/class
Picasso.with(context)
.load(imageUrl)
.into(myImage, new ImageLoadedCallback(progressBar) {
@Override
public void onSuccess() {
if (this.progressBar != null) {
this.progressBar.setVisibility(View.GONE);
}
}
});
inside your adapter/class as above I create an inner class for the callback:
private class ImageLoadedCallback implements Callback {
ProgressBar progressBar;
public ImageLoadedCallback(ProgressBar progBar){
progressBar = progBar;
}
@Override
public void onSuccess() {
}
@Override
public void onError() {
}
}
Hope this makes sense!
回答2:
I implemented the progress dialog till the image download and its very simple. Take your ImageView in relative layout and place progress loader on same image view. Apply the below code and handle progress dialog visibility only.
holder.loader.setVisibility(View.VISIBLE);
holder.imageView.setVisibility(View.VISIBLE);
final ProgressBar progressView = holder.loader;
Picasso.with(context)
.load(image_url)
.transform(new RoundedTransformation(15, 0))
.fit()
.into(holder.imageView, new Callback() {
@Override
public void onSuccess() {
progressView.setVisibility(View.GONE);
}
@Override
public void onError() {
// TODO Auto-generated method stub
}
});
}
Hope it will help someone! :)
回答3:
Its very simple to show the progress bar.
Add this code to the activity to load the image with progress bar.
Picasso.with(this)
.load(hoteImageStr)
.error(R.drawable.loading)
.into(img, new com.squareup.picasso.Callback() {
@Override
public void onSuccess() {
if (progress != null) {
progress .setVisibility(View.GONE);
}
}
@Override
public void onError() {
}
});
Add this to your layout file.
<RelativeLayout
android:id="@+id/hoteldetails_myContainer"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<ProgressBar
android:id="@+id/hoteldetails_progressBar"
style="?android:attr/progressBarStyleSmall"
android:layout_width="50dp"
android:layout_height="50dp"
android:layout_gravity="center"
android:visibility="gone"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:layout_marginTop="20dp"
android:layout_marginBottom="20dp" />
<ImageView
android:id="@+id/hoteldetails_imageView1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:scaleType="fitXY"
/>
</RelativeLayout>
回答4:
first create a drawable layout like this:
progress_animation.xml:
<?xml version="1.0" encoding="utf-8"?>
<animated-rotate xmlns:android="http://schemas.android.com/apk/res/android"
android:drawable="@drawable/loading"
android:pivotX="50%"
android:pivotY="50%"/>
add loading.png to drawable
Usage:
Picasso.with(context).load(imageUri).placeholder(R.drawable.progress_animation).into(imgView);
回答5:
Kotlin
val circularProgressDrawable = CircularProgressDrawable(context)
circularProgressDrawable.strokeWidth = 5f
circularProgressDrawable.centerRadius = 30f
circularProgressDrawable.start()
Picasso.get().load(imageUrl).placeholder(circularProgressDrawable).into(holder.imageView)
The above code eliminates xml code and it's clean.
回答6:
You should setup your ProgressBar in addition to the Picasso library and you should manage the visibility of it manually using listeners.
I am using UniversalImageLoader and the Picasso library should be very similiar.
private ImageLoadingListener photoSuccess = new ImageLoadingListener() {
@Override
public void onLoadingStarted(String imageUri, View view) {
}
@Override
public void onLoadingFailed(String imageUri, View view,
FailReason failReason) {
if(progress != null)
progress.setVisibility(View.GONE);
}
@Override
public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {
if(progress != null)
progress.setVisibility(View.GONE);
if(mImage != null)
mImage.setVisibility(View.VISIBLE);
}
@Override
public void onLoadingCancelled(String imageUri, View view) {
}
};
来源：https://stackoverflow.com/questions/22143157/android-picasso-placeholder-and-error-image-styling