picasso 毕加索 是sequre公司开源的一个图片缓存库,(sequre公司是一个技术很nb的公司 开源项目有retrofit okhttp等众多优秀开源项目) 毕加索github地址
1:可以实现图片下载和缓存功能
2:picasso 已经解决了adapter中错位问题
3:复杂的图片进行压缩,尽量减少内存的消耗
4:实现内存缓存和二级硬盘缓存的效果
picasso 框架解决下载中遇到的问题:
1:在adapter中回收和取消当前下载
2: 使用最少的内存完成图片的转换
3: 自动内存和硬盘缓存
4:图形转换,比如大小,旋转
5:加载网络资源和本地资源
依赖:
compile 'com.squareup.picasso:picasso:2.5.2'
代码混淆: -dontwarn com.squareup.okhttp.**
使用教程网址 http://square.github.io/picasso/
加载图片的方式很多 可以是网络可以是本地
Picasso.with(context).load(R.drawable.landing_screen).into(imageView1); Picasso.with(context).load("file:///android_asset/DvpvklR.png").into(imageView2); Picasso.with(context).load(new File(...)).into(imageView3);
例子1:加载网络图片:
package com.example.pic_picasso; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.util.Log; import android.view.View; import android.widget.ImageView; import com.squareup.picasso.Callback; import com.squareup.picasso.Picasso; public class MainActivity extends AppCompatActivity { ImageView imageView; public String imgUrl="http://img2.ph.126.net/-JWI_lNvXoHo4fxVDLADBg==/6597137936377058906.jpg"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); imageView= (ImageView) findViewById(R.id.imgview); } public void onLoadImage(View view) { // Picasso.with(view.getContext()).load(imgUrl).into(imageView); Picasso.with(view.getContext()).load(imgUrl).into(imageView, new Callback() { @Override public void onSuccess() { Log.d("------","加载成功"); } @Override public void onError() { Log.d("------","加载失败"); } }); } }
例子2:毕加索 在adapter中的加载和取消 这里选择recyclerView
package com.example.pic_picasso; import android.os.Bundle; import android.support.annotation.Nullable; import android.support.v7.app.AppCompatActivity; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.ImageView; import android.widget.TextView; import com.squareup.picasso.Picasso; import java.util.ArrayList; import java.util.List; /** * Created by asange on 16/6/5. */ public class LoadInRecyclerViewActivity extends AppCompatActivity { RecyclerView rcyclerView; MyAdapter adapter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_recyclerview); rcyclerView= (RecyclerView) findViewById(R.id.rcyclerView); rcyclerView.setLayoutManager(new LinearLayoutManager(this)); adapter=new MyAdapter(); rcyclerView.setAdapter(adapter); List<String> urls=new ArrayList<>(); for(int i=0;i<30;i++) { urls.add("http://m.weather.com.cn/img/b"+i+".gif"); } adapter.bindData(true,urls); } class MyAdapter extends RecyclerView.Adapter<MyAdapter.Myholder> { private final List<String> urls=new ArrayList<>(); public void bindData(boolean isRefresh,List<String> datas) { if(isRefresh) urls.clear(); urls.addAll(datas); notifyDataSetChanged(); } @Override public Myholder onCreateViewHolder(ViewGroup parent, int viewType) { return new Myholder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recyclerview,parent,false)); } @Override public void onBindViewHolder(Myholder holder, int position) { Picasso.with(holder.imageView.getContext()).load(urls.get(position)).into(holder.imageView); holder.textView.setText("pos:"+position); } @Override public void onViewRecycled(Myholder holder) { super.onViewRecycled(holder); //取消 Picasso.with(holder.imageView.getContext()).cancelRequest(holder.imageView); } @Override public int getItemCount() { return urls.size(); } public class Myholder extends RecyclerView.ViewHolder { public ImageView imageView; public TextView textView; public Myholder(View itemView) { super(itemView); imageView= (ImageView) itemView.findViewById(R.id.icon); textView= (TextView) itemView.findViewById(R.id.title); } } } }
例子3:裁剪图片(可自定义宽度和高度)
public void onLoadImageResize(View v) { String url="http://www.77mv.com/uploads/allimg/c151025/1445M15H2P40-12224.jpg"; Picasso.with(v.getContext()).load(url).resize(100,100).into(imageView); }
裁剪效果图:
居中裁剪
public void onLoadImageResize(View v) { String url="http://www.77mv.com/uploads/allimg/c151025/1445M15H2P40-12224.jpg"; Picasso.with(v.getContext()).load(url).resize(100,100).centerCrop().into(imageView); }
运行效果:
例4: 占位符 (图片加载成功之前显示的图片 加载失败显示的图片)
加载前的图片 如果加载失败 不替换 加载成功才替换
public void onLoadImagePlaceholder(View v) { String url="null";//注定加载失败 Picasso.with(v.getContext()).load(url).placeholder(R.mipmap.ic_launcher).fit().into(imageView); }
加载前的图片 加载成功替换成功图片 加载失败替换失败的图片
public void onLoadImagePlaceholder(View v) { String url="null";//注定加载失败 //Picasso.with(v.getContext()).load(url).placeholder(R.mipmap.ic_launcher).fit().into(imageView); Picasso.with(v.getContext()).load(url).placeholder(R.mipmap.ic_launcher).error(R.mipmap.ic_error).fit().into(imageView); }
例5:对图片的自定义裁剪
public void onLoadImageMyCut(View view){ String url="http://www.77mv.com/uploads/allimg/c151025/1445M15H2P40-12224.jpg"; Picasso.with(view.getContext()).load(url).transform(new MyTrans(url)).into(imageView); } class MyTrans implements Transformation { public String key; public MyTrans(String key) { this.key=key; } @Override public Bitmap transform(Bitmap source) { //1/2 裁剪 int size = Math.min(source.getWidth(), source.getHeight()); int x = (source.getWidth() - size) / 2; int y = (source.getHeight() - size) / 2; Bitmap result = Bitmap.createBitmap(source, x, y, size, size); if (result != source) { source.recycle(); } return result; } @Override public String key() {//唯一的key return key; } }
正方形图片:
class MyTrans implements Transformation { public String key; public MyTrans(String key) { this.key=key; } @Override public Bitmap transform(Bitmap source) { int sequre = Math.min(source.getWidth(), source.getHeight()); Bitmap resultSequre = Bitmap.createBitmap(source, sequre, sequre, source.getWidth(),source.getHeight()); if (resultSequre != source) { source.recycle(); } return resultSequre; } @Override public String key() {//唯一的key return key; } }