我尝试使用Web服务和AsyncTask连接到mysql

Question

我试图通过webservice连接到mysql数据库（所以a。php中的特定url）并使用AsyncTask。

运行应用程序时出错并关闭，告诉我＆＃34;不幸的是发生了错误＆＃34;

没有日志读得很好，因此我请求帮助，Aque也开始在android中编程。

感谢您的帮助。

MainActivity.java

    package com.example.pruebaenviarvariables;

    import java.io.IOException;
    import java.io.UnsupportedEncodingException;
    import java.util.ArrayList;
    import java.util.List;

    import org.apache.http.NameValuePair;
    import org.apache.http.client.ClientProtocolException;
    import org.apache.http.client.HttpClient;
    import org.apache.http.client.entity.UrlEncodedFormEntity;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.impl.client.DefaultHttpClient;
    import org.apache.http.message.BasicNameValuePair;

    import android.app.Activity;
    import android.content.pm.ActivityInfo;
    import android.os.AsyncTask;
    import android.os.Bundle;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.ImageButton;
    import android.widget.Toast;

    import com.example.pruebaenviarvariables.R;

    public class MainActivity extends Activity {
        private EditText dni;
        private EditText nombre;
        private EditText telefono;
        private EditText email;
        private Button insertar;
        private Button mostrar;
        private ImageButton mas;
        private ImageButton menos;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR_PORTRAIT);
            setContentView(R.layout.activity_main);

            EditText dni=(EditText)findViewById(R.id.dni);
            EditText nombre=(EditText)findViewById(R.id.nombre);
            EditText telefono=(EditText)findViewById(R.id.telefono);
            EditText email=(EditText)findViewById(R.id.email);      
            //Insertamos los datos de la persona.
            Button insertar=(Button)findViewById(R.id.insertar);    
            insertar.setOnClickListener(new OnClickListener(){

                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub

                        new Insertar(MainActivity.this).execute();      

                }

            });

        }

        //Inserta los datos de las Personas en el servidor.
            private boolean insertar(){  
                HttpClient httpclient;
                List<NameValuePair> nameValuePairs;
                HttpPost httppost;
                httpclient=new DefaultHttpClient();
                httppost= new HttpPost("http://192.168.0.11/pruebaAndroid/insert.php"); // Url del Servidor      
                //Añadimos nuestros datos
                nameValuePairs = new ArrayList<NameValuePair>(4);
                nameValuePairs.add(new BasicNameValuePair("dni",dni.getText().toString().trim()));
                nameValuePairs.add(new BasicNameValuePair("nombre",nombre.getText().toString().trim()));
                nameValuePairs.add(new BasicNameValuePair("telefono",telefono.getText().toString().trim()));
                nameValuePairs.add(new BasicNameValuePair("email",email.getText().toString().trim()));

                try {
                   httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
                   httpclient.execute(httppost);
                   return true;
                } catch (UnsupportedEncodingException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (ClientProtocolException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                return false;
            }       
            //AsyncTask para insertar Personas
            class Insertar extends AsyncTask<String,String,String>{

                private Activity context;

                Insertar(Activity context){
                    this.context=context;
                }
                @Override
                protected String doInBackground(String... params) {
                    // TODO Auto-generated method stub
                    if(insertar())
                        context.runOnUiThread(new Runnable(){
                            @Override
                            public void run() {
                                // TODO Auto-generated method stub                          
                                Toast.makeText(context, "Persona insertada con éxito", Toast.LENGTH_LONG).show();
                                nombre.setText("");
                                dni.setText("");
                                telefono.setText("");
                                email.setText("");
                            }                       
                        });
                    else
                        context.runOnUiThread(new Runnable(){
                            @Override
                            public void run() {
                                // TODO Auto-generated method stub                          
                                Toast.makeText(context, "Persona no insertada con éxito", Toast.LENGTH_LONG).show();
                            }                   
                        });
                      return null;
                }           
            }
    }

fragment_main.xml的代码

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:background="@android:color/white" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="nombre" />

    <EditText
        android:id="@+id/nombre"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10" 
        android:inputType="text">

        <requestFocus />
    </EditText>

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="dni" />

    <EditText
        android:id="@+id/dni"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="text" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="tlf" />

    <EditText
        android:id="@+id/telefono"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="number" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="email" />

    <EditText
        android:id="@+id/email"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="textEmailAddress" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <Button
            android:id="@+id/insertar"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="2"
            android:text="insertar" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp" >

    </LinearLayout>

</LinearLayout>

最后，日志：

    6 21:20:43.371: D/AndroidRuntime(1163): Shutting down VM
    07-06 21:20:43.371: W/dalvikvm(1163): threadid=1: thread exiting with uncaught exception (group=0xb3a5bba8)
    07-06 21:20:43.391: E/AndroidRuntime(1163): FATAL EXCEPTION: main
    07-06 21:20:43.391: E/AndroidRuntime(1163): Process: com.example.pruebaenviarvariables, PID: 1163
    07-06 21:20:43.391: E/AndroidRuntime(1163): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.pruebaenviarvariables/com.example.pruebaenviarvariables.MainActivity}: java.lang.NullPointerException
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at android.os.Handler.dispatchMessage(Handler.java:102)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at android.os.Looper.loop(Looper.java:136)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at android.app.ActivityThread.main(ActivityThread.java:5017)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at java.lang.reflect.Method.invokeNative(Native Method)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at java.lang.reflect.Method.invoke(Method.java:515)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at dalvik.system.NativeStart.main(Native Method)
    07-06 21:20:43.391: E/AndroidRuntime(1163): Caused by: java.lang.NullPointerException
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at com.example.pruebaenviarvariables.MainActivity.onCreate(MainActivity.java:51)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at android.app.Activity.performCreate(Activity.java:5231)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
    07-06 21:20:43.391: E/AndroidRuntime(1163):     ... 11 more
    07-06 21:20:46.851: I/Process(1163): Sending signal. PID: 1163 SIG: 9

Answer 1

在类级别定义了所有布局变量（EditText，Button等）。在onCreate（）方法中，您没有使用这些对象并重新创建它。因此，您在onCreate（）中创建和设置对象不适用于UI线程。 UI线程只访问类级变量。

解决方案：不要在oncreate（）中重新定义相同的布局变量，在此方法中使用类级别对象。

MainActivity代码：

    private EditText dni;
    private EditText nombre;
    private EditText telefono;
    private EditText email;
    private Button insertar;
    private Button mostrar;
    private ImageButton mas;
    private ImageButton menos;
    private EditText dni;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR_PORTRAIT);
        setContentView(R.layout.activity_main);

        dni=(EditText)findViewById(R.id.dni);
        nombre=(EditText)findViewById(R.id.nombre);
        telefono=(EditText)findViewById(R.id.telefono);
        email=(EditText)findViewById(R.id.email);      
        //Insertamos los datos de la persona.
        insertar=(Button)findViewById(R.id.insertar);

//其他代码.......

xml文件：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/LinearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:background="@android:color/white" >

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="nombre" />

<EditText
    android:id="@+id/nombre"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:ems="10" 
    android:inputType="text">

    <requestFocus />
</EditText>

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="dni" />

<EditText
    android:id="@+id/dni"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:ems="10"
    android:inputType="text" />

<TextView
    android:id="@+id/textView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="tlf" />

<EditText
    android:id="@+id/telefono"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:ems="10"
    android:inputType="number" />

<TextView
    android:id="@+id/textView3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="email" />

<EditText
    android:id="@+id/email"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:ems="10"
    android:inputType="textEmailAddress" />

    <Button
        android:id="@+id/insertar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:text="insertar" />


<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="20dp" >

</LinearLayout>

</LinearLayout>