我创建了一个可在单击按钮后从url读取数据的应用。
然后，我使用这些数据在新活动中显示其中一些。
通过使用ASynctask如下读取URL：
line-height主要代码如下：
package com.example.test;
import android.os.AsyncTask;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
public class Read_URL extends AsyncTask<Void,Void,Void> {
String data = "";
String [] list;
ArrayList <String> hiscore_skill_rank = new ArrayList<>();
ArrayList <String> hiscore_skill_level = new ArrayList<>();
ArrayList <String> hiscore_skill_exp = new ArrayList<>();
@Override
protected Void doInBackground(Void... voids) {
try {
URL url = new URL("https://......");
HttpURLConnection httpURLConnection =(HttpURLConnection) url.openConnection();
InputStream inputStream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
String line;
for (int j = 0; j <24; j++) {
line = bufferedReader.readLine();
data = data + line;
list = line.split(",");
hiscore_skill_rank.add(list[0]);
hiscore_skill_level.add(list[1]);
hiscore_skill_exp.add(list[2]);
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
}
}
process.execute的结果是3个24个变量的数组列表。
我的问题是，当我启动该应用程序时，它崩溃了，但是当我以调试模式启动它时，一切正常。
我在想，也许是因为在常规模式下读取URL需要花费时间，所以它不知道显示什么，但是在调试模式下，它有更多时间来完成从url获取信息的操作。
如果没有完成读取数据的操作，读取URL会导致应用崩溃吗？
谢谢！
答案 0 :(得分：0)
问题在于此方法：
public void openHiScore(){
Read_URL process = new Read_URL();
process.execute();
Intent intent = new Intent(this,HiScore.class);
intent.putStringArrayListExtra("hiscore_skill_rank",process.hiscore_skill_rank);
intent.putStringArrayListExtra("hiscore_skill_level",process.hiscore_skill_level);
intent.putStringArrayListExtra("hiscore_skill_exp",process.hiscore_skill_exp);
intent.putExtra("name",name.getText().toString());
startActivity(intent);
}
process.execute（）将启动异步任务，但随后在doInBackground代码运行之前立即继续创建新的Intent。如果可能，您应该尝试将所有Intent / startActivity代码移至Read_URL类的onPostEvent中。或者，在您的主活动中创建一个回调函数，Read_Url可以从onPostEvent调用该回调函数，该函数将把Main中的所有Intent / startActivity东西都做完。
这里是如何集成回调函数的示例。为了简化操作，我将Read_URL设置为在MainActivity类内部定义的内部类。
MainActivity.java
// Imports from MainActivity
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
// Imports from Read_URL
import android.os.AsyncTask;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
Button button;
EditText name;
public Activity myActivity;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.opening_screen);
button = findViewById(R.id.continue_button);
name = findViewById(R.id.username_text);
myActivity = this;
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
openHiScore();
}
});
}
public void openHiScore(){
Read_URL process = new Read_URL();
process.execute();
}
public void processResults(ArrayList hiscore_skill_rank, ArrayList hiscore_skill_level, ArrayList hiscore_skill_exp) {
Intent intent = new Intent(this,HiScore.class);
intent.putStringArrayListExtra("hiscore_skill_rank",hiscore_skill_rank);
intent.putStringArrayListExtra("hiscore_skill_level",hiscore_skill_level);
intent.putStringArrayListExtra("hiscore_skill_exp",hiscore_skill_exp);
intent.putExtra("name",name.getText().toString());
startActivity(intent);
}
// I think you can include the Read_URL class inside of your MainActivity class
// In that way, it can access the public variables declared in the MainActivity class
public class Read_URL extends AsyncTask<Void,Void,Void> {
String data = "";
String [] list;
ArrayList <String> hiscore_skill_rank = new ArrayList<>();
ArrayList <String> hiscore_skill_level = new ArrayList<>();
ArrayList <String> hiscore_skill_exp = new ArrayList<>();
@Override
protected Void doInBackground(Void... voids) {
try {
URL url = new URL("https://......");
HttpURLConnection httpURLConnection =(HttpURLConnection) url.openConnection();
InputStream inputStream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
String line;
for (int j = 0; j <24; j++) {
line = bufferedReader.readLine();
data = data + line;
list = line.split(",");
hiscore_skill_rank.add(list[0]);
hiscore_skill_level.add(list[1]);
hiscore_skill_exp.add(list[2]);
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
myActivity.processResults(hiscore_skill_rank, hiscore_skill_level, hiscore_skill_exp);
}
} // end of Read_URL
} // end of MainActivity