详解android写一个选择图片的示例代码

public class mainactivity extends appcompatactivity implements adapterview.onitemclicklistener, adapterview.onitemlongclicklistener, imageadapter.onimagechecklistener, view.onclicklistener {

  private static final int camera_code = 12;
  list<file> filelist = new arraylist<>();
  imageadapter adapter;

  gridview gvimage;
  textview tvfinish;


  @override
  protected void oncreate(bundle savedinstancestate) {
    super.oncreate(savedinstancestate);
    setcontentview(r.layout.activity_main);
    initview();
    //弹出对话框，加载数据
    loaddata();
  }

  private void initview() {
    gvimage = (gridview) findviewbyid(r.id.gv_image);
    tvfinish = (textview) findviewbyid(r.id.tv_finish);


    adapter = new imageadapter(this, filelist);
    adapter.setonimagechecklistener(this);
    gvimage.setadapter(adapter);
    gvimage.setonitemclicklistener(this);
    gvimage.setonitemlongclicklistener(this);

    tvfinish.setonclicklistener(this);
  }

  private progressdialog showprogressdialog() {
    //弹出对话框
    progressdialog dialog = new progressdialog(this);
    dialog.settitle("提示");
    dialog.setmessage("正在加载图片，请稍等。。。");
    dialog.show();
    return dialog;
  }

  private void loaddata() {
    final progressdialog dialog = showprogressdialog();
    //开启线程
    new thread() {
      @override
      public void run() {
        super.run();
        //递归
        //从sd卡中获取所有图片
        getfile(environment.getexternalstoragedirectory());
        runonuithread(new runnable() {
          @override
          public void run() {
            dialog.dismiss();
            adapter.notifydatasetchanged();
          }
        });
      }
    }.start();
  }

  public void getfile(file dir) {
    //1. 获取子目录
    file[] files = dir.listfiles();
    if (files == null)
      return;
    //集合或者数组去点for
    for (file file : files) {
      if (file.isdirectory())
        getfile(file);
      else {
        //加载图片
        if (file.getname().endswith(".png") || file.getname().endswith(".jpg")) {
          filelist.add(file);
        }
      }

    }
  }

  file camerafile;

  //点击
  @override
  public void onitemclick(adapterview<?> parent, view view, int position, long id) {
    if (position == 0) {
      //getabsolutepath返回的路径是没有"/"
      camerafile = new file(environment.getexternalstoragedirectory().getabsolutepath() + "/dcim/" + system.currenttimemillis() + ".png");
      //打开照相机
      intent intent = new intent(mediastore.action_image_capture);
      //照相机需要带数据
      intent.putextra(mediastore.extra_output, uri.fromfile(camerafile));
      startactivityforresult(intent, camera_code);
    } else {
      //打开大图
      file file = filelist.get(position - 1);
      //带数据跳转到现实大图
      intent intent = new intent(this, showbigimage.class);
      intent.putextra("file", file);
      startactivity(intent);
    }
  }


  @override
  protected void onactivityresult(int requestcode, int resultcode, intent data) {
    super.onactivityresult(requestcode, resultcode, data);
    log.e("tag", resultcode + "---------------------");
    if (requestcode == camera_code && resultcode == result_ok) {
      log.e("tag", (camerafile.exists()) + "");
      filelist.add(0, camerafile);
      adapter.notifydatasetchanged();
    }
  }

  //长按
  @override
  public boolean onitemlongclick(adapterview<?> parent, view view, int position, long id) {
    if (position == 0)
      return false;
    else {
      adapter.open(position);
    }
    return true;
  }

  @override
  public void onimagecheck(boolean b) {
    //b代表 适配器中 有没有勾选的值
    tvfinish.setenabled(b);

  }

  @override
  public void onclick(view v) {
    //需要知道有哪些数据被选中
    //不能使用泛型，arraylist才实现了序列化，list没有实现
    arraylist<file> resultlist = new arraylist<>();
    //通过适配器中的 为true的 选中的项来加载file
    sparsebooleanarray booleanarray = adapter.getbooleanarray();
    for (int i = 0; i < booleanarray.size(); i++) {
      boolean ischeck = booleanarray.get(booleanarray.keyat(i));
      if (ischeck) {
        int position = booleanarray.keyat(i);
        resultlist.add(filelist.get(position - 1));
      }
    }
    intent intent = new intent();
    intent.putextra("list", resultlist);
    //返回数据
    setresult(result_ok, intent);
    finish();
  }
}

public class imageadapter extends listitemadapter<file> {

  private boolean select = false;


  public void open(int posisiont) {
    select = true;
    booleanarray.put(posisiont, true);
    if (onimagechecklistener != null)
      onimagechecklistener.onimagecheck(true);
    this.notifydatasetchanged();
  }

  public void close() {
    select = false;
    booleanarray.clear();
    notifydatasetchanged();
  }

  //position
  //hashmap<integer, boolean> map = new hashmap<>();

  private sparsebooleanarray booleanarray = new sparsebooleanarray();

  public sparsebooleanarray getbooleanarray() {
    return booleanarray;
  }

  public imageadapter(context context, list<file> list) {
    super(context, list);
  }

  @override
  public int getcount() {
    //多出来的就是照相机
    return super.getcount() + 1;
  }

  //  @override
//  public view getview(int position, view convertview, viewgroup parent) {
//    if (convertview == null) {
//      imageview iv = new imageview(mcontext);
//      iv.setscaletype(imageview.scaletype.center_crop);
//      iv.setbackgroundcolor(color.argb(0xff, 0x07, 0x05, 0x18));
//      int width = mcontext.getresources().getdisplaymetrics().widthpixels / 3 - 2;
//      gridview.layoutparams params = new gridview.layoutparams(width, width);
//      iv.setpadding(2, 2, 2, 2);
//      iv.setlayoutparams(params);
//      convertview = iv;
//    }
//    imageview iv = (imageview) convertview;
//    if (position == 0) {
//      //照相机
//      iv.setimageresource(r.mipmap.camera);
//    } else {
//      iv.setimageuri(uri.fromfile(getitem(position - 1)));
//    }
//    return convertview;
//  }
  @override
  public view getview(final int position, view convertview, viewgroup parent) {
    viewholder holder;
    if (convertview == null) {
      convertview = view.inflate(mcontext, r.layout.item_image, null);
      holder = new viewholder(convertview);
      convertview.settag(holder);
    } else {
      holder = (viewholder) convertview.gettag();
    }
    if (position == 0) {
      holder.image.setimageresource(r.mipmap.camera);
      holder.checkbox.setvisibility(view.gone);
    } else {
      holder.image.setimageuri(uri.fromfile(getitem(position - 1)));
      if (select) {
        holder.checkbox.setvisibility(view.visible);
        //当前的需不需要勾选呢
        //null
        boolean b = booleanarray.get(position);
        if (b == null || b == false) {
          holder.checkbox.setchecked(false);
        } else {
          holder.checkbox.setchecked(true);
        }
        //item点击和布局冲突
        holder.checkbox.setonclicklistener(new view.onclicklistener() {
          @override
          public void onclick(view v) {
            boolean b = booleanarray.get(position);
            if (b == null || b == false)
              b = true;
            else
              b = false;
            booleanarray.put(position, b);
            //判断所有的boolean，如果已经没有一个true 关闭
            for (int i = 0; i < booleanarray.size(); i++) { //4-true 0==false
              //两个值 key -- > 3 4
              // 0 1 2 3 4 5
              boolean ischecked = booleanarray.get(booleanarray.keyat(i));
              log.e("tag", "----" + ischecked);
              log.e("tag", booleanarray.tostring());
              if (ischecked) {
                //有被勾选的值
                if (onimagechecklistener != null)
                  onimagechecklistener.onimagecheck(true);
                return;
              }
            }
            if (onimagechecklistener != null)
              onimagechecklistener.onimagecheck(false);
            //没有被勾选的值了
            //关闭
            close();
          }
        });
      } else {
        holder.checkbox.setvisibility(view.gone);
      }
      //不能使用oncheck
//      holder.checkbox.setoncheckedchangelistener(new compoundbutton.oncheckedchangelistener() {
//        @override
//        public void oncheckedchanged(compoundbutton buttonview, boolean ischecked) {
//          booleanarray.put(position, ischecked);
//        }
//      });
    }
    return convertview;
  }


  //回调方法。
  //写在需要执行方法的地方
  //他实现 在需要返回的地方
  public interface onimagechecklistener {
    public void onimagecheck(boolean b);
  }

  private onimagechecklistener onimagechecklistener;

  //alt+insert

  public void setonimagechecklistener(onimagechecklistener onimagechecklistener) {
    this.onimagechecklistener = onimagechecklistener;
  }

  class viewholder {
    imageview image;
    checkbox checkbox;

    public viewholder(view convertview) {
      image = (imageview) convertview.findviewbyid(r.id.iv_image);
      int width = mcontext.getresources().getdisplaymetrics().widthpixels / 3 - 2;
      relativelayout.layoutparams params = new relativelayout.layoutparams(width, width);
      image.setlayoutparams(params);
      checkbox = (checkbox) convertview.findviewbyid(r.id.cb_check);
    }


  }
}

//也可以用 extends 来限制一个泛型的父类
//在类的后面定义一个泛型
public abstract class listitemadapter<t> extends baseadapter {

  protected context mcontext;
  protected list<t> mlist;

  //必须要有上下文，数据
  //list<file> list<string>
  public listitemadapter(context context, list<t> list) {
    mcontext = context;
    mlist = list;
  }

  //适配器去加载一个list
  public void setlist(list<t> list) {
    this.mlist = list;
    notifydatasetchanged();
  }

  @override
  public int getcount() {
    return mlist == null ? 0 : mlist.size();
  }

  @override
  public t getitem(int position) {
    return mlist.get(position);
  }

  @override
  public long getitemid(int position) {
    return position;
  }
}

public class showbigimage extends appcompatactivity {


  @override
  protected void oncreate(@nullable bundle savedinstancestate) {
    super.oncreate(savedinstancestate);
    imageview iv = new imageview(this);
    file file = (file) getintent().getserializableextra("file");
    iv.setimageuri(uri.fromfile(file));
    setcontentview(iv);
  }
}

<?xml version="1.0" encoding="utf-8"?>
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:id="@+id/activity_main"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical"
  tools:context="com.example.administrator.imageselector.mainactivity">

  <relativelayout
    android:layout_width="match_parent"
    android:layout_height="50dp"
    android:background="@color/colorprimary">

    <textview
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerinparent="true"
      android:text="选取图片"
      android:textcolor="@android:color/white"
      android:textsize="18sp" />

    <textview
      android:id="@+id/tv_finish"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignparentright="true"
      android:layout_centervertical="true"
      android:layout_marginright="10dp"
      android:enabled="false"
      android:text="完成"
      android:textcolor="@color/textenable" />
  </relativelayout>

  <gridview
    android:id="@+id/gv_image"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:horizontalspacing="2dp"
    android:numcolumns="3"
    android:verticalspacing="2dp" />
</linearlayout>

<?xml version="1.0" encoding="utf-8"?>
<relativelayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:background="#03030a">

  <imageview
    android:id="@+id/iv_image"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="5dp"
    android:scaletype="centercrop"
    android:src="@mipmap/camera" />

  <checkbox
    android:id="@+id/cb_check"
    android:button="@null"
    android:layout_width="20dp"
    android:layout_height="20dp"
    android:background="@drawable/cb_selector"
    android:layout_alignparentright="true"
    android:layout_margin="10dp"
    />

</relativelayout>

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:color="@android:color/white" android:state_enabled="true" />
  <item android:color="@android:color/darker_gray" android:state_enabled="false" />
</selector>