@rookiedev is right, there's no load(Bitmap) in Glide，原因是：获取Bitmap 通常需要时间，有时还会阻塞 I/O。因此，在 UI 线程上调用 imageWithText 并不是一个好习惯。 更新：话虽如此，我不久前提出了this feature；虽然黑客更容易做到，但您可以在下面找到我强烈推荐的“滑翔方式”。
Glide 被设计成灵活的，这个问题很好地展示了这个特性。以下实现可能看起来很长，但所有部分都有其存在的理由。考虑到性能提升，将生成器放入 Glide 世界的代码量并不多。我尝试将其格式化为简短，折叠不相关的部分并使用更短的静态导入（请参阅导入的结尾）。
代码还包括以编程方式生成的 UI，因此您只需将以下所有代码复制粘贴到 GlideGeneratedImageListFragment.java 并运行它；唯一的外部依赖是支持库的RecyclerView。
class GeneratingAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
// See https://docs.google.com/drawings/d/1KyOJkNd5Dlm8_awZpftzW7KtqgNR6GURvuF6RfB210g/edit?usp=sharing
// ModelType/A, DataType/T, ResourceType/Z, TranscodeType/R
private final GenericRequestBuilder<GenerateParams, GenerateParams, Bitmap, GlideDrawable> generator;
public GeneratingAdapter(final Context context) {
generator = Glide // this part should be cleaner in Glide 4.0, but that's not released yet
.with(context)
.using(new GenerateParamsPassthroughModelLoader(), GenerateParams.class) // custom class
.from(GenerateParams.class)
.as(Bitmap.class)
.transcode(new BitmapToGlideDrawableTranscoder(context), GlideDrawable.class) // builtin
.decoder(new GenerateParamsBitmapResourceDecoder(context)) // custom class
.encoder(new BitmapEncoder(Bitmap.CompressFormat.PNG, 0/*ignored for lossless*/)) // builtin
.cacheDecoder(new FileToStreamDecoder<Bitmap>(new StreamBitmapDecoder(context))) // builtin
//.placeholder(new ColorDrawable(Color.YELLOW)) // you can pre-set placeholder and error
.error(new ColorDrawable(Color.RED)) // so it's easier when binding
//.diskCacheStrategy(DiskCacheStrategy.NONE) // only for debugging to always regenerate
//.skipMemoryCache(true) // only for debugging to always regenerate
;
}
@Override public int getItemCount() { return 1000; }
private final float[] colorCache = new float[] {0, 1.0f, 0.5f};
private final float[] bgCache = new float[] {0, 0.5f, 1.0f};
@Override public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
colorCache[0] = bgCache[0] = (position * 15) % 360; // just to have a fancy example :)
GenerateParams params = new GenerateParams(
// omit position to see Glide caching in action (every 24th item / 12th row is the same)
"android text"/* + " #" + position*/,
Color.HSVToColor(colorCache),
Color.HSVToColor(bgCache)
);
generator/*.clone() in case you see weird behavior*/.load(params).into((ImageView)holder.itemView);
}
@Override public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
int height = parent.getContext().getResources().getDisplayMetrics().heightPixels / 3;
ImageView view = new ImageView(parent.getContext());
view.setLayoutParams(new RecyclerView.LayoutParams(MATCH_PARENT, height));
view.setScaleType(ImageView.ScaleType.FIT_CENTER);
return new RecyclerView.ViewHolder(view) {}; // anon class for brevity
}
}
public class GlideGeneratedImageListFragment extends Fragment {
@Override public @Nullable View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
RecyclerView view = new RecyclerView(container.getContext());
view.setLayoutParams(new MarginLayoutParams(MATCH_PARENT, MATCH_PARENT));
view.setLayoutManager(new GridLayoutManager(container.getContext(), 2 /*columns*/));
view.setAdapter(new GeneratingAdapter(view.getContext()));
return view;
}
}
/** Extracted params from imageWithText, but left some hardcoded values like 20sp/bold/center in {@link Generators}. */
class GenerateParams {
final String text;
final int color;
final int background;
public GenerateParams(String text, int color, int bg) {
this.text = text;
this.color = color;
this.background = bg;
}
public String getId() {
// TODO make sure it's unique for every possible instance of GenerateParams
// because it will affect how the resulting bitmap is cached
// the below is correct correct for the current fields, if those change this has to change
return String.format(Locale.ROOT, "%s-%08x-%08x", text, color, background);
}
}
/** Boilerplate because of the degeneration in ModelType == DataType, but important for caching.
* @see GeneratingAdapter#generator */
class GenerateParamsPassthroughModelLoader implements ModelLoader<GenerateParams, GenerateParams> {
@Override public DataFetcher<GenerateParams> getResourceFetcher(final GenerateParams model, int width, int height) {
return new DataFetcher<GenerateParams>() {
@Override public GenerateParams loadData(Priority priority) throws Exception { return model; }
@Override public void cleanup() { }
@Override public String getId() { return model.getId(); }
@Override public void cancel() { }
};
}
}
/** Handles pooling to reduce/prevent GC lagging from too many {@link Bitmap#createBitmap}s */
class GenerateParamsBitmapResourceDecoder implements ResourceDecoder<GenerateParams, Bitmap> {
private final Context context;
public GenerateParamsBitmapResourceDecoder(Context context) { this.context = context; }
@Override public Resource<Bitmap> decode(GenerateParams source, int width, int height) throws IOException {
BitmapPool pool = Glide.get(context).getBitmapPool();
Bitmap bitmap = pool.getDirty(width, height, Bitmap.Config.ARGB_8888);
if (bitmap == null) {
bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
}
Generators.imageWithTextNoLayout(context, bitmap, source);
return BitmapResource.obtain(bitmap, pool);
}
@Override public String getId() {
// be careful if you change the Generator implementation you have to change this
// otherwise the users may see a cached image; or clear cache on app update
return "com.example.MyImageGenerator";
}
}
class Generators {
/** OP's original implementation fixed for real centering */
public static Bitmap imageWithText(Context context, Bitmap bitmap, GenerateParams params) {
TextView view = new TextView(context);
view.setText(params.text);
view.setTextColor(params.color);
view.setBackgroundColor(params.background);
view.setTypeface(null, Typeface.BOLD);
view.setGravity(Gravity.CENTER);
view.setTextSize(20 /*sp*/);
Canvas canvas = new Canvas(bitmap);
view.measure(makeMeasureSpec(canvas.getWidth(), EXACTLY), makeMeasureSpec(canvas.getHeight(), EXACTLY));
view.layout(0, 0, canvas.getWidth(), canvas.getHeight());
view.draw(canvas);
return bitmap;
}
/** Generate centered text without creating a View, more lightweight.
* Consider https://stackoverflow.com/a/8369690/253468 for multiline support. */
public static Bitmap imageWithTextNoLayout(Context context, Bitmap bitmap, GenerateParams params) {
Paint paint = new Paint();
paint.setColor(params.color);
paint.setTextAlign(Paint.Align.CENTER); // text's anchor for the x given in drawText
paint.setTextSize(applyDimension(COMPLEX_UNIT_SP, 20, context.getResources().getDisplayMetrics()));
paint.setTypeface(Typeface.DEFAULT_BOLD);
Canvas canvas = new Canvas(bitmap);
canvas.drawColor(params.background);
canvas.drawText(params.text, canvas.getWidth() / 2, canvas.getHeight() / 2, paint);
return bitmap;
}
}
// Here are the imports in case you need it;
// didn't want to put it in the beginning to keep the relevant code first.
import java.io.IOException;
import java.util.Locale;
import android.content.Context;
import android.graphics.*;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.*;
import android.view.*;
import android.view.ViewGroup.MarginLayoutParams;
import android.widget.*;
import static android.util.TypedValue.*;
import static android.view.View.MeasureSpec.*;
import static android.view.ViewGroup.LayoutParams.*;
import com.bumptech.glide.*;
import com.bumptech.glide.load.ResourceDecoder;
import com.bumptech.glide.load.data.DataFetcher;
import com.bumptech.glide.load.engine.Resource;
import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
import com.bumptech.glide.load.model.ModelLoader;
import com.bumptech.glide.load.resource.bitmap.*;
import com.bumptech.glide.load.resource.drawable.GlideDrawable;
import com.bumptech.glide.load.resource.file.FileToStreamDecoder;
import com.bumptech.glide.load.resource.transcode.BitmapToGlideDrawableTranscoder;
这是它的样子（真正的滚动要流畅得多，GIF 的 FPS 真的很低）：
注意它是如何加载前几项的，然后逐渐加载其余的。内存缓存和池预热需要一点时间，但如果您想要更流畅的显示，可以使用预加载器。加热后，它很好地滚动。操作栏上的删除按钮调用Glide.clearDiskCache() 和Glide.clearMemory()，因此它再次开始重新生成项目。