listview載入圖片過程中，圖片載入不一致原理。
阿新 • • 發佈：2018-11-28
//主介面佈局
<?xml version="1.0" encoding="utf-8"?> <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity"> <Button android:layout_width="0dp" android:layout_height="wrap_content" android:id="@+id/buthttp" app:layout_constraintTop_toTopOf="parent" app:layout_constraintLeft_toLeftOf="parent" android:text="http" android:onClick="getHttpData" app:layout_constraintRight_toRightOf="parent"/> <Button android:layout_width="0dp" android:layout_height="wrap_content" android:id="@+id/butclient" app:layout_constraintTop_toBottomOf="@id/buthttp" app:layout_constraintLeft_toLeftOf="parent" android:text="client" app:layout_constraintRight_toRightOf="parent"/> <ListView android:layout_width="0dp" android:layout_height="0dp" app:layout_constraintTop_toBottomOf="@id/butclient" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintBottom_toBottomOf="parent" android:id="@+id/listview" ></ListView> </android.support.constraint.ConstraintLayout>
//子條目佈局
<?xml version="1.0" encoding="utf-8"?> <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" xmlns:app="http://schemas.android.com/apk/res-auto"> <TextView android:layout_width="0dp" android:layout_height="100dp" app:layout_constraintTop_toTopOf="parent" app:layout_constraintRight_toLeftOf="@id/imageview" app:layout_constraintLeft_toLeftOf="parent" android:id="@+id/textview1" /> <TextView android:layout_width="0dp" android:layout_height="100dp" app:layout_constraintTop_toBottomOf="@id/textview1" app:layout_constraintRight_toLeftOf="@id/imageview" app:layout_constraintLeft_toLeftOf="parent" android:id="@+id/textview2" /> <ImageView android:layout_width="150dp" android:layout_height="200dp" app:layout_constraintRight_toRightOf="parent" android:id="@+id/imageview" /> </android.support.constraint.ConstraintLayout>
//主函式MainActivity
package com.example.rikao1106; import android.os.AsyncTask; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.ListView; import java.util.List; public class MainActivity extends AppCompatActivity { private Button buttonhttp,buttonclient; private ListView listView; private String path = "http://api.expoon.com/AppNews/getNewsList/type/1/p/1"; private MyBaseAdafter adafter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); listView = findViewById(R.id.listview); adafter = new MyBaseAdafter(MainActivity.this); listView.setAdapter(adafter); findViewById(R.id.buthttp).setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Utils.getRequest2(path, Bean.class, new Utils.BeanResultCallback2<Bean>() { @Override public void onSuccess(Bean object) { adafter.setListData(object.getData()); } }); /*new AsyncTask<String,Void,List<Bean.DataBean>>(){ @Override protected List<Bean.DataBean> doInBackground(String... strings) { List<Bean.DataBean> dataBeans = Utils.httpMode(strings[0]); return dataBeans; } @Override protected void onPostExecute(List<Bean.DataBean> dataBeans) { adafter.setListData(dataBeans); } }.execute(path);*/ } }); } private void requestData() { Utils.getRequest2("", Bean.class, new Utils.BeanResultCallback() { @Override public void onSuccess(Object object) { Bean bean = (Bean) object; } }); } /*private void getHttpData(View v){ new AsyncTask<String,Void,List<Bean.DataBean>>(){ @Override protected List<Bean.DataBean> doInBackground(String... strings) { List<Bean.DataBean> dataBeans = Utils.httpMode(strings[0]); return dataBeans; } @Override protected void onPostExecute(List<Bean.DataBean> dataBeans) { adafter.setListData(dataBeans); } }.execute(path); }*/ }
//新建一個bean類
package com.example.rikao1106;
import java.util.List;
public class Bean {
private List<DataBean> data;
public List<DataBean> getData() {
return data;
}
public void setData(List<DataBean> data) {
this.data = data;
}
public static class DataBean {
private String news_title;
private String news_summary;
private String pic_url;
public String getNews_title() {
return news_title;
}
public void setNews_title(String news_title) {
this.news_title = news_title;
}
public String getNews_summary() {
return news_summary;
}
public void setNews_summary(String news_summary) {
this.news_summary = news_summary;
}
public String getPic_url() {
return pic_url;
}
public void setPic_url(String pic_url) {
this.pic_url = pic_url;
}
}
}
//建立介面卡
package com.example.rikao1106;
import android.content.Context;
import android.graphics.Bitmap;
import android.os.AsyncTask;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
public class MyBaseAdafter extends BaseAdapter {
private Context context;
private List<Bean.DataBean>mlist;
public MyBaseAdafter(Context context) {
this.context = context;
mlist = new ArrayList<>();
}
public void setListData(List<Bean.DataBean> list){
this.mlist = list;
notifyDataSetChanged();
}
@Override
public int getCount() {
return mlist.size();
}
@Override
public Bean.DataBean getItem(int position) {
return mlist.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
final ViewHoder viewHoder;
if(convertView==null){
convertView = LayoutInflater.from(context).inflate(R.layout.item,parent,false);
viewHoder = new ViewHoder();
viewHoder.textView1 = convertView.findViewById(R.id.textview1);
viewHoder.textView2 = convertView.findViewById(R.id.textview2);
viewHoder.imageView = convertView.findViewById(R.id.imageview);
convertView.setTag(viewHoder);
}else{
viewHoder = (ViewHoder) convertView.getTag();
}
viewHoder.textView1.setText(mlist.get(position).getNews_title());
viewHoder.textView2.setText(mlist.get(position).getNews_summary());
//RxJava
//載入圖片
/*new AsyncTask<String,Void,Bitmap>(){
@Override
protected Bitmap doInBackground(String... strings) {
Bitmap bitmp = Utils.getBitmp(strings[0]);
return bitmp;
}
@Override
protected void onPostExecute(Bitmap bitmap) {
viewHoder.imageView.setImageBitmap(bitmap);
}
}.execute(mlist.get(position).getPic_url());*/
//外面呼叫簡單了
//還有一個錯亂問題
//Utils.getBitmap(getItem(position).getPic_url(), viewHoder.imageView);
/*
假設imageView(0)第一次進來載入1.jpg圖片
往上滑動,imageView(0)滑出去
底下一個view進來
複用imageView(0)載入1.jpg圖片沒有完成
給imageView(0)載入4.jpg圖片
imageView(0)有兩個任務
imageView(0)可能顯示1.jpg也可能顯示4.jpg.發生錯亂
*/
/*
每次載入圖片時url和imageView繫結
*/
//第一次繫結1.jpg
//第二次從新繫結到4.jpg
//後用的把先用的頂掉
//載入前繫結:外部做的
viewHoder.imageView.setTag(getItem(position).getPic_url());
//viewHoder.imageView.setTag(0, "");
//Utils內部不只到繫結細節.沒辦法直接載入圖片給ImageView
//外部來做,顯示圖片:需要關注什麼(Bitmap, 當前bitmap圖片的url路徑)
Utils.getBitmap(getItem(position).getPic_url(), new Utils.Callback() {
//按照合同實現
@Override
public void loadImageSuccess(String imageUrl, Bitmap bitmap) {
if(imageUrl.equals(viewHoder.imageView.getTag())) {
viewHoder.imageView.setImageBitmap(bitmap);
} else {
Log.i("TEST", "錯亂: " );
}
}
});
return convertView;
}
class ViewHoder{
private TextView textView1,textView2;
private ImageView imageView;
}
}
//工具類
package com.example.rikao1106;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.telecom.Call;
import android.widget.ImageView;
import com.google.gson.Gson;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.ProtocolException;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
public class Utils {
//獲取網路連線
public static List<Bean.DataBean> httpMode (String path){
try {
HttpURLConnection urlConnection = (HttpURLConnection) new URL(path).openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setReadTimeout(5000);
urlConnection.setConnectTimeout(5000);
if(urlConnection.getResponseCode()==200){
//呼叫轉換字串方法
String string = getString(urlConnection.getInputStream());
Bean bean = new Gson().fromJson(string, Bean.class);
List<Bean.DataBean> data = bean.getData();
return data;
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
/* public static List<Bean.DataBean> clientMode (String s){
//請求配置
RequestConfig custom = RequestConfig
.custom()
.setConnectTimeout(5000)
.build();
//建立HttpClient
CloseableHttpClient custom1 = HttpClients
.custom()
.setDefaultRequestConfig(custom)
.build();
//建立請求物件
HttpUriRequest request = (HttpUriRequest) RequestBuilder
.get()
.setUri(strings[0])
.build();
//執行一個請求
try {
HttpResponse response = custom1.execute(request);
int statusCode = response.getStatusLine().getStatusCode();
if(statusCode == 200){
String json = EntityUtils.toString(response.getEntity());
//得到gson
Bean bean = new Gson().fromJson(json, Bean.class);
List<Bean.DataBean> data = bean.getData();
return data;
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}*/
public static void getBitmap(final String imageUrl, final Callback callback) {
new AsyncTask<String, Void, Bitmap>(){
@Override
protected Bitmap doInBackground(String... strings) {
return getBitmp(strings[0]);
}
@Override
protected void onPostExecute(Bitmap bitmap) {
//按照合同執行
callback.loadImageSuccess(imageUrl, bitmap);
}
}.execute(imageUrl);
}
//把執行緒吞掉
//因為是非同步操作,不知道什麼時候返回bitmap.所以不能直接返回結果
//載入圖片大部分情況下是為了展示
public static void getBitmap(String imgUrl, final ImageView imageView) {
/////
new AsyncTask<String,Void,Bitmap>(){
////////
@Override
protected Bitmap doInBackground(String... strings) {
return Utils.getBitmp(strings[0]);
}
@Override
protected void onPostExecute(Bitmap bitmap) {
imageView.setImageBitmap(bitmap);
}
}.execute(imgUrl);
}
/**
* 介面 相當於合同
*/
public interface Callback {
public void loadImageSuccess(String imageUrl, Bitmap bitmap);
}
//網路請求一張圖片
public static Bitmap getBitmp (String path){
try {
HttpURLConnection urlConnection = (HttpURLConnection) new URL(path).openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setReadTimeout(5000);
urlConnection.setConnectTimeout(5000);
if(urlConnection.getResponseCode()==200){
//呼叫轉換字串方法
Bitmap bitmap = BitmapFactory.decodeStream(urlConnection.getInputStream());
return bitmap;
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
public interface BeanResultCallback2<T> {
void onSuccess(T object);
}
public static void getRequest2(String url, final Class clazz, final BeanResultCallback2 callback) {
new AsyncTask<String, Void, Object>(){
@Override
protected Object doInBackground(String... strings) {
return getRequest(strings[0], clazz);
}
@Override
protected void onPostExecute(Object o) {
callback.onSuccess(o);
}
}.execute(url);
}
public interface BeanResultCallback {
void onSuccess(Object object);
}
public static void getRequest2(String url, final Class clazz, final BeanResultCallback callback) {
new AsyncTask<String, Void, Object>(){
@Override
protected Object doInBackground(String... strings) {
return getRequest(strings[0], clazz);
}
@Override
protected void onPostExecute(Object o) {
callback.onSuccess(o);
}
}.execute(url);
}
//執行一個get請求,返回bean
public static <T> T getRequest(String url, Class clazz) {
String result = getRequest(url);
T t = (T) new Gson().fromJson(result, clazz);
return t;
}
//執行一個get請求,返回String結果
public static String getRequest(String url) {
String result = "";
try {
HttpURLConnection urlConnection = (HttpURLConnection) new URL(url).openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setReadTimeout(5000);
urlConnection.setConnectTimeout(5000);
if(urlConnection.getResponseCode()==200){
//呼叫轉換字串方法
result = getString(urlConnection.getInputStream());
}
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
public static String getString(InputStream is) throws IOException {
StringBuilder builder = new StringBuilder();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
for (String i = bufferedReader.readLine();i != null;i=bufferedReader.readLine()){
builder.append(i);
}
return builder.toString();
}
}