1.添加网络授权
<uses-permission android:name="android.permission.INTERNET"/>
2.UI的主线程中不能直接访问网络
3.异步任务操作
public class MainActivity extends AppCompatActivity {
private Button button;
private ImageView imageView;
private String image_path = "";
private ProgressDialog dialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = this.findViewById(R.id.button1);
imageView = this.findViewById(R.id.imageView1);
dialog = new ProgressDialog(this);
dialog.setTitle("提示信息");
dialog.setMessage("正在下载图片");
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new MyTask().execute(image_path);
}
});
}
/**
* 路径、刻度、返回值类型
*/
public class MyTask extends AsyncTask<String, Void, Bitmap> {
// 执行任务之前的操作
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog.show();
}
// 完成耗时操作
@Override
protected Bitmap doInBackground(String... params) {
return null;
}
//更新UI操作
@Override
protected void onPostExecute(Bitmap bitmap) {
super.onPostExecute(bitmap);
}
}
}
