Android Studio，应用停止工作

Question

我是 Android Studio 的新手。我按照 Youtube 和 Google 错误的教程进行操作，但这次我似乎无法找到解决此问题的方法。

我正在创建一个使用 mysql 数据库的简单登录和注册应用程序。当我启动该应用程序并单击注册按钮时，该应用程序关闭并显示:“应用程序已停止工作”。

我检查了 logcat 并发现了这个:

09-13 17:23:19.607    2229-2236/com.example.appname.appname E/art﹕ Failed sending reply to debugger: Broken pipe
09-13 17:23:47.756    2229-2229/com.example.appname.appname E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.appname.appname, PID: 2229
    java.lang.IllegalStateException: Could not find method userReg(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.widget.Button
            at android.view.View$DeclaredOnClickListener.resolveMethod(View.java:4479)
            at android.view.View$DeclaredOnClickListener.onClick(View.java:4443)
            at android.view.View.performClick(View.java:5198)
            at android.view.View$PerformClick.run(View.java:21147)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5417)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

主 Activity .java

import android.app.Activity;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
public void userReg()
{
    startActivity(new Intent(this, Register.class));
}
    public void userLogin(View view)
    {


    }


}

注册.java

import android.app.Activity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;

public class Register extends Activity {
    EditText ET_NAME,ET_USER_NAME,ET_USER_PASS;
    String name,user_name,user_pass;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.register_layout);
        ET_NAME = (EditText) findViewById(R.id.name);
        ET_USER_NAME = (EditText) findViewById(R.id.new_user_name);
        ET_USER_PASS = (EditText) findViewById(R.id.new_user_pass);
    }

    public void userReg(View view)
    {
        name = ET_NAME.getText().toString();
        user_name = ET_USER_NAME.getText().toString();
        user_pass = ET_USER_PASS.getText().toString();
        String method = "register";
        BackgroundTask backgroundTask = new BackgroundTask(this);
        backgroundTask.execute(method,name,user_name,user_pass);
        finish();
    }
}

后台任务.java

import android.content.Context;
import android.os.AsyncTask;
import android.widget.Toast;

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;

public class BackgroundTask extends AsyncTask<String, Void, String> {
    Context ctx;
    BackgroundTask(Context ctx)
    {
        this.ctx=ctx;

    }
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params) {
        String reg_url = "http://10.0.2.2.2/webapp/register.php";
        String login_url = "http://10.0.2.2.2/webapp/login.php";
        String method = params[0];
        if(method.equals("register"))
        {
        String name = params [1];
            String user_name = params[2];
            String user_pass = params[3];
            try {
                URL url = new URL(reg_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                OutputStream OS = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter (new OutputStreamWriter(OS, "UTF-8"));
            String data = URLEncoder.encode("user", "UTF-8") +"=" +URLEncoder.encode(name, "UTF-8") + "&"+
                    URLEncoder.encode("user_name", "UTF-8") +"=" +URLEncoder.encode(user_name, "UTF-8") + "&"+
                    URLEncoder.encode("user_pass", "UTF-8") +"=" +URLEncoder.encode(user_pass, "UTF-8");
                bufferedWriter.write(data);
                bufferedWriter.flush();
                bufferedWriter.close();
                OS.close();
                InputStream IS = httpURLConnection.getInputStream();
                IS.close();
                return "Registration Success..";
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return null;
    }

    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
    }

    @Override
    protected void onPostExecute(String result) {
        Toast.makeText(ctx,result,Toast.LENGTH_LONG).show();
    }
}

Answer 1

改变你的Mainactivity.java

public void userReg()
{
    startActivity(new Intent(this, Register.class));
}

到

public void userReg(View v)
{
    startActivity(new Intent(Mainactivity.this, Register.class));
}

并且在 Register.java

public void userReg(View view)
{
    name = ET_NAME.getText().toString();
    user_name = ET_USER_NAME.getText().toString();
    user_pass = ET_USER_PASS.getText().toString();
    String method = "register";
    BackgroundTask backgroundTask = new BackgroundTask(this);
    backgroundTask.execute(method,name,user_name,user_pass);
    finish();
}

到

public void userReg(View view)
{
    name = ET_NAME.getText().toString();
    user_name = ET_USER_NAME.getText().toString();
    user_pass = ET_USER_PASS.getText().toString();
    String method = "register";
    BackgroundTask backgroundTask = new BackgroundTask(Register.this);
    backgroundTask.execute(method,name,user_name,user_pass);
    finish();
}