android - 在没有联系人图像可用时显示图像

Question

我编写了一个应用程序，可以简单地显示手机上所有可用的联系人。该应用程序运行良好。它可以检索联系人图像和显示名称。但是，在滚动列表时，应用程序有些滞后。我想知道如何消除这种滞后。同时，我想在没有联系人图像时显示图像。我试图制作一个 bool 标志，告诉我接触图像光标是否为空，如果是，那么我将标志 (image_found) 设置为 false，然后尝试使用 setImageResource 设置图像，但它没有用。好吧，然后我认为当没有图像时，blob 对象可能会得到一个 null，但它也起作用了。这是我的 mail_activity 代码。

package legacy_systems.aggregatedcontactlist;

import java.util.ArrayList;
import java.util.List;

import android.os.Bundle;
import android.provider.ContactsContract;
import android.support.v4.widget.CursorAdapter;
import android.support.v4.widget.SimpleCursorAdapter;
import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.view.Menu;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

public class MainActivity extends ListActivity{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Cursor c = getContentResolver().query(ContactsContract.Contacts.CONTENT_URI, 
                                              null, 
                                              null, 
                                              null, 
                                              ContactsContract.Contacts.DISPLAY_NAME+" ASC");

        ArrayList<String> con_ids = new ArrayList<String>();
        if(c!=null)
        {
            for(c.moveToFirst();!c.isAfterLast();c.moveToNext()){
                con_ids.add(c.getString(c.getColumnIndex(ContactsContract.Contacts._ID)));
            }
        }



        ListView ls = getListView();

        MyAdapter ada = new MyAdapter(this, R.layout.listview, con_ids);

        ls.setAdapter(ada);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }


}

这是 MyAdapter 的代码

package legacy_systems.aggregatedcontactlist;

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import android.content.ContentUris;
import android.content.Context;
import android.content.pm.PackageManager.NameNotFoundException;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.provider.ContactsContract;
import android.provider.ContactsContract.Contacts;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;


public class MyAdapter extends ArrayAdapter<String>{
    Context cont;
    boolean image_found = true;
    ArrayList<String> ids;

    public MyAdapter(Context context, int resource,
            ArrayList<String> objects) {
        super(context, resource, objects);
        cont = context;
        ids = objects;
        // TODO Auto-generated constructor stub
    }

    public View getView(int position, View ConvertView, ViewGroup parent){
        //For Contact Photo
        Bitmap photo=null;
        //Inflator Work
        LayoutInflater infl = (LayoutInflater)cont.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View row = infl.inflate(R.layout.list_view, parent, false);

        //Retreiving photo and Setting Photo
        photo = BitmapFactory.decodeStream(retrievePhoto(ids.get(position)));
        ImageView iv = (ImageView)row.findViewById(R.id.listicon);
        iv.setImageBitmap(photo);

        if(!image_found)
        {
            iv.setImageResource(R.drawable.person);
        }

        //Retrieving ContactName
        TextView tv  =(TextView)row.findViewById(R.id.listtext);
        tv.setText(retrieveName(ids.get(position)));

        return row;
    }

    private InputStream retrievePhoto(String Id)
    {
        Uri ContactUri = ContentUris.withAppendedId(Contacts.CONTENT_URI, Long.valueOf(Id));
        Uri PhotoUri = Uri.withAppendedPath(ContactUri, Contacts.Photo.CONTENT_DIRECTORY);

        Cursor c = cont.getContentResolver().query(PhotoUri, new String[]{Contacts.Photo.PHOTO}, null,null,null);

        try
        {
            if(c.moveToFirst())
            {
                byte[] data = c.getBlob(0);
                if(data!=null)
                {
                    return new ByteArrayInputStream(data);
                }
                else
                {
                    image_found = false;
                }
            }
        }
        finally
        {
            c.close();
        }
        return null;
    }

    private String retrieveName(String Id)
    {
        Uri ContactUri = ContentUris.withAppendedId(Contacts.CONTENT_URI, Long.valueOf(Id));
        Cursor c = cont.getContentResolver()
                        .query(ContactUri, 
                                new String[]{ContactsContract.Contacts.DISPLAY_NAME}, 
                                null, 
                                null, 
                                null);
        if(c==null)
            return null;
        try
        {
            if(c.moveToFirst())
            {
                String name = c.getString(0);
                return name;
            }
        }
        finally
        {
            c.close();
        }
        return null;
    }

}

我真的很高兴我能走到这一步。请帮助我继续我的事业。

[编辑]我已经实现了建议的事情，现在我无法检索单个联系人图像。我不知道是什么问题。我只在 MyAdapter.java 中进行了更改，我正在发布它的代码。

package legacy_systems.aggregatedcontactlist;

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.List;

import android.content.ContentUris;
import android.content.Context;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.res.Resources;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.AsyncTask;
import android.provider.ContactsContract;
import android.provider.ContactsContract.Contacts;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;


public class MyAdapter extends ArrayAdapter<String>{
    Context cont;
    boolean image_found = true;
    ArrayList<String> ids;

    public MyAdapter(Context context, int resource,
            ArrayList<String> objects) {
        super(context, resource, objects);
        cont = context;
        ids = objects;
        // TODO Auto-generated constructor stub
    }

    public View getView(int position, View ConvertView, ViewGroup parent){

        View row = ConvertView;
        //For Contact Photo
        Bitmap photo=null;
        //Inflator Work
        if(row==null)
        {
            LayoutInflater infl = (LayoutInflater)cont.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row = infl.inflate(R.layout.list_view, parent, false);
        }

        //Retreiving photo and Setting Photo
        ImageView iv = (ImageView)row.findViewById(R.id.listicon);


        synchronized (iv) {
            Uri contactUri = ContentUris.withAppendedId(Contacts.CONTENT_URI, Long.valueOf(ids.get(position)));
            PhotoLoader loader = new PhotoLoader(iv, contactUri);
            loader.execute();

        }



        //Retrieving ContactName
        TextView tv  =(TextView)row.findViewById(R.id.listtext);
        tv.setText(retrieveName(ids.get(position)));

        return row;
    }



    private String retrieveName(String Id)
    {
        Uri ContactUri = ContentUris.withAppendedId(Contacts.CONTENT_URI, Long.valueOf(Id));
        Cursor c = cont.getContentResolver()
                        .query(ContactUri, 
                                new String[]{ContactsContract.Contacts.DISPLAY_NAME}, 
                                null, 
                                null, 
                                null);
        if(c==null)
            return null;
        try
        {
            if(c.moveToFirst())
            {
                String name = c.getString(0);
                return name;
            }
        }
        finally
        {
            c.close();
        }
        return null;
    }

    class PhotoLoader extends AsyncTask<Void, Void, Bitmap>
    {
        final WeakReference<ImageView> mView;
        final Uri mUri;

        public PhotoLoader(ImageView view, Uri uri) {

            if(view == null)
            {
                throw new IllegalArgumentException("View Cannot be null");
            }
            if(uri == null)
            {
                throw new IllegalArgumentException("Uri cant be null");
            }
            mView = new WeakReference<ImageView>(view);
            mUri = uri;
        }

        protected Bitmap doInBackground(Void...args){
            Bitmap bitmap;
            InputStream in = ContactsContract.Contacts.openContactPhotoInputStream(cont.getContentResolver(), mUri);
            bitmap = BitmapFactory.decodeStream(in);

            if(bitmap == null)
            {   Resources mResources = cont.getResources();
                bitmap = BitmapFactory.decodeResource(mResources, R.drawable.person);
            }
            return bitmap;
        }
    }

}

我还没有实现缓存。当这个问题解决后，我会尝试实现缓存和持有者。在那之前，请解决问题，

[重新编辑]这次。图片全乱了。

package legacy_systems.aggregatedcontactlist;

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.List;

import android.content.ContentUris;
import android.content.Context;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.res.Resources;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.AsyncTask;
import android.provider.ContactsContract;
import android.provider.ContactsContract.Contacts;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;


public class MyAdapter extends ArrayAdapter<String>{
    Context cont;
    boolean image_found = true;
    ArrayList<String> ids;
    ImageView iv;

    public MyAdapter(Context context, int resource,
            ArrayList<String> objects) {
        super(context, resource, objects);
        cont = context;
        ids = objects;
        // TODO Auto-generated constructor stub
    }

    public View getView(int position, View ConvertView, ViewGroup parent){

        View row = ConvertView;
        //For Contact Photo

        //Inflator Work

        if(row==null)
        {
            LayoutInflater infl = (LayoutInflater)cont.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row = infl.inflate(R.layout.list_view, parent, false);
        }


        //Retreiving photo and Setting Photo
        iv = (ImageView)row.findViewById(R.id.listicon);


        synchronized (this) {
            Uri contactUri = ContentUris.withAppendedId(Contacts.CONTENT_URI, Long.valueOf(ids.get(position)));
            PhotoLoader loader = new PhotoLoader(iv, contactUri);
            loader.execute();

        }



        //Retrieving ContactName
        TextView tv  =(TextView)row.findViewById(R.id.listtext);
        tv.setText(retrieveName(ids.get(position)));

        return row;
    }



    private String retrieveName(String Id)
    {
        Uri ContactUri = ContentUris.withAppendedId(Contacts.CONTENT_URI, Long.valueOf(Id));
        Cursor c = cont.getContentResolver()
                        .query(ContactUri, 
                                new String[]{ContactsContract.Contacts.DISPLAY_NAME}, 
                                null, 
                                null, 
                                null);
        if(c==null)
            return null;
        try
        {
            if(c.moveToFirst())
            {
                String name = c.getString(0);
                return name;
            }
        }
        finally
        {
            c.close();
        }
        return null;
    }

    class PhotoLoader extends AsyncTask<Void, Void, Bitmap>
    {
        final WeakReference<ImageView> mView;
        final Uri mUri;

        public PhotoLoader(ImageView view, Uri uri) {

            if(view == null)
            {
                throw new IllegalArgumentException("View Cannot be null");
            }
            if(uri == null)
            {
                throw new IllegalArgumentException("Uri cant be null");
            }
            mView = new WeakReference<ImageView>(view);
            mUri = uri;
        }

        protected Bitmap doInBackground(Void...args){
            Bitmap bitmap;
            InputStream in = ContactsContract.Contacts.openContactPhotoInputStream(cont.getContentResolver(), mUri);
            bitmap = BitmapFactory.decodeStream(in);


            return bitmap;
        }

        protected void onPostExecute(Bitmap bitmap)
        {
            if(bitmap == null)
            {   Resources mResources = cont.getResources();
                bitmap = BitmapFactory.decodeResource(mResources, R.drawable.person);
                iv.setImageBitmap(bitmap);
                return;
            }
            iv.setImageBitmap(bitmap);
        }
    }

}

Answer 1

除了 Gabe Sechan 所说的 View 每次都被夸大之外，您还应该更改一些内容。不要使用内容提供者获取照片，而是使用 Contacts 类中的 openContachPhotoInputStream 方法，您可以找到 here .您还应该使用 AsyncTask 将位图的打开和加载移动到后台线程。最后，尝试使用 LruCache 来缓存已经打开的位图以提高效率，如描述的那样 here .我最近不得不做类似的事情，所以我分享了一段代码来帮助你。我用它来加载背景上的图像。

class PhotoLoader extends AsyncTask<Void, Void, Bitmap> {

    final WeakReference<ImageView> mView;
    final Uri mUri;

    PhotoLoader(ImageView view, Uri uri) {
        if (view == null) {
            throw new IllegalArgumentException("View cannot be null!");
        }

        if (uri == null) {
            throw new IllegalArgumentException("Uri cannot be null!");
        }

        mView = new WeakReference<ImageView>(view);
        mUri = uri;
    }

    @Override
    protected Bitmap doInBackground(Void... args) {
                    // use the uri passed to the constructor
        InputStream is = Contacts.openContactPhotoInputStream(mResolver,
                mUri);
        Bitmap bm = BitmapFactory.decodeStream(is);

                    // load custom resource image if contact has no photo
        if (bm == null) {
            bm = BitmapFactory.decodeResource(mResources,
                    R.drawable.ic_contact);
        }

        return bm;
    }

    @Override
    protected void onPostExecute(Bitmap result) {
                    // use a transition drawable for nice fade effect
        Drawable[] layers = new Drawable[2];
        layers[0] = mResources.getDrawable(android.R.color.transparent);

        layers[1] = new BitmapDrawable(mResources, result);
        TransitionDrawable t = new TransitionDrawable(layers);
        t.setCrossFadeEnabled(true);

        ImageView view = mView.get();

        if(view != null) {
            view.setImageDrawable(t);
            t.startTransition(mShortAnimation);
        }
        synchronized (mPhotoCache) {
                            // store bitmap in LruCache for later use...
            mPhotoCache.put(mUri.toString(), result);
        }
    }
}

我在我的适配器中这样使用它:

synchronized (mPhotoCache) {
    Bitmap b = mPhotoCache.get(key);

    if (b != null) {
    imageView.setImageBitmap(b);
    } else {
    imageView.setImageResource(android.R.color.transparent);
    PhotoLoader loader = new PhotoLoader(imageView, uri);
    loader.execute();
    }
}

编辑:澄清一下，我使用字符串格式的联系人 uri 作为缓存键。在检查缓存之前的某处适配器中，我有以下行:字符串键 = uri.toString();