如何使用asyncTask
/**
* asyncTask ---是sdk中提供好的異步任務代碼, 我們可以用它來代替handler
* ctrl+o 重寫方法
*/
public class MainActivity extends AppCompatActivity {
public String urlString = "http://api.expoon.com/AppNews/getNewsList/type/1/p/1";
String urlBitmap = "https://img-my.csdn.net/uploads/201407/26/1406383265_8550.jpg";
private ListView listView;
ArrayList<Product.DataBean> dataBeanList = new ArrayList();// 集合爲空;
private MAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.lv);
//直接調用asyncTask類請求網絡,把url傳進去
mAdapter = new MAdapter();
listView.setAdapter(mAdapter);
/**
* 這行代碼要在主線程調用;,execute裏面的參數是接口地址;讓async請求網絡,並更新UI;
* 1 不用開子線程,
* 2 不用寫handler;
* 因爲asynctask底層原理就是用的Thread+handler幫我們把事情做了;
*
*/
new MAsyncTask().execute(urlString);
}
/**
* 處理異步任務
* 泛型 1---傳遞過來的參數類型
* 2--進度
* 3--返回值得類型
*/
class MAsyncTask extends AsyncTask<String,Void,String>{
/**
* 這個方法運行在子線程;讓他去請求網絡,
* @param strings 可變參數;
* @return
*/
@Override
protected String doInBackground(String... strings) {
String stringUrl = strings[0];
String netJson = NetUtil.getNetJson(stringUrl);
return netJson;
}
/**
*onPostExecute這個方法是運行在主線程,可以更新UI;
*
* @param netJson 這個參數s 就是doInBackground返回值;
*/
@Override
protected void onPostExecute(String netJson) {
super.onPostExecute(netJson);
Gson gson = new Gson();
Product product = gson.fromJson(netJson, Product.class);
dataBeanList.addAll(product.getData());
mAdapter.notifyDataSetChanged();//可以直接更新適配器,因爲這個方法是在主線程
}
}
private class MAdapter extends BaseAdapter {
@Override
public int getCount() {
Log.e("wzq", "getCount:" + dataBeanList.size());
return dataBeanList.size();
}
@Override
public Object getItem(int i) {
return dataBeanList.get(i);
}
@Override
public long getItemId(int i) {
return i;
}
@Override
public View getView(int i, View view, ViewGroup viewGroup) {
View view1 = View.inflate(MainActivity.this, R.layout.item02, null);
TextView tv_name = view1.findViewById(R.id.tv_name);
ImageView iv = view1.findViewById(R.id.iv);
tv_name.setText(dataBeanList.get(i).getNews_summary());
new MBitmapAsyncTask(iv).execute(dataBeanList.get(i).getPic_url());
Log.e("wzq", "getCount:" + "執行getview");
return view1;
}
}
/**
* 用asyncTask請求服務器圖片
*/
private class MBitmapAsyncTask extends AsyncTask<String,Void,Bitmap>{
ImageView iv;
public MBitmapAsyncTask(ImageView iv) {
this.iv = iv;
}
@Override
protected Bitmap doInBackground(String... strings) {
Bitmap mbitmap = NetUtil.getNetBitmap(strings[0]);
return mbitmap;
}
@Override
protected void onPostExecute(Bitmap bitmap) {
super.onPostExecute(bitmap);
//大膽的更新ui,因爲這是主線程
iv.setImageBitmap(bitmap);
}
}
* asyncTask ---是sdk中提供好的異步任務代碼, 我們可以用它來代替handler
* ctrl+o 重寫方法
*/
public class MainActivity extends AppCompatActivity {
public String urlString = "http://api.expoon.com/AppNews/getNewsList/type/1/p/1";
String urlBitmap = "https://img-my.csdn.net/uploads/201407/26/1406383265_8550.jpg";
private ListView listView;
ArrayList<Product.DataBean> dataBeanList = new ArrayList();// 集合爲空;
private MAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.lv);
//直接調用asyncTask類請求網絡,把url傳進去
mAdapter = new MAdapter();
listView.setAdapter(mAdapter);
/**
* 這行代碼要在主線程調用;,execute裏面的參數是接口地址;讓async請求網絡,並更新UI;
* 1 不用開子線程,
* 2 不用寫handler;
* 因爲asynctask底層原理就是用的Thread+handler幫我們把事情做了;
*
*/
new MAsyncTask().execute(urlString);
}
/**
* 處理異步任務
* 泛型 1---傳遞過來的參數類型
* 2--進度
* 3--返回值得類型
*/
class MAsyncTask extends AsyncTask<String,Void,String>{
/**
* 這個方法運行在子線程;讓他去請求網絡,
* @param strings 可變參數;
* @return
*/
@Override
protected String doInBackground(String... strings) {
String stringUrl = strings[0];
String netJson = NetUtil.getNetJson(stringUrl);
return netJson;
}
/**
*onPostExecute這個方法是運行在主線程,可以更新UI;
*
* @param netJson 這個參數s 就是doInBackground返回值;
*/
@Override
protected void onPostExecute(String netJson) {
super.onPostExecute(netJson);
Gson gson = new Gson();
Product product = gson.fromJson(netJson, Product.class);
dataBeanList.addAll(product.getData());
mAdapter.notifyDataSetChanged();//可以直接更新適配器,因爲這個方法是在主線程
}
}
private class MAdapter extends BaseAdapter {
@Override
public int getCount() {
Log.e("wzq", "getCount:" + dataBeanList.size());
return dataBeanList.size();
}
@Override
public Object getItem(int i) {
return dataBeanList.get(i);
}
@Override
public long getItemId(int i) {
return i;
}
@Override
public View getView(int i, View view, ViewGroup viewGroup) {
View view1 = View.inflate(MainActivity.this, R.layout.item02, null);
TextView tv_name = view1.findViewById(R.id.tv_name);
ImageView iv = view1.findViewById(R.id.iv);
tv_name.setText(dataBeanList.get(i).getNews_summary());
new MBitmapAsyncTask(iv).execute(dataBeanList.get(i).getPic_url());
Log.e("wzq", "getCount:" + "執行getview");
return view1;
}
}
/**
* 用asyncTask請求服務器圖片
*/
private class MBitmapAsyncTask extends AsyncTask<String,Void,Bitmap>{
ImageView iv;
public MBitmapAsyncTask(ImageView iv) {
this.iv = iv;
}
@Override
protected Bitmap doInBackground(String... strings) {
Bitmap mbitmap = NetUtil.getNetBitmap(strings[0]);
return mbitmap;
}
@Override
protected void onPostExecute(Bitmap bitmap) {
super.onPostExecute(bitmap);
//大膽的更新ui,因爲這是主線程
iv.setImageBitmap(bitmap);
}
}
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