Question

当我尝试启动我的应用程序时，一切正常，但是当我从菜单中打开一个类时，它无法打开。我刚接触到android编程。求你帮帮我..谢谢你

不断收到此消息

不幸的是，（App Name）已停止。“

这是我的java

package com.e_attendance;

import android.app.Activity;
import android.app.AlertDialog.Builder;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class ManageClass extends Activity implements OnClickListener
{

    EditText editClassno;
    Button btnAdd, btnDelete, btnModify, btnViewAll;
    SQLiteDatabase db;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.classdetail);

        editClassno = (EditText) findViewById(R.id.editClassno);
        btnAdd.setOnClickListener(this);
        btnDelete.setOnClickListener(this);
        btnModify.setOnClickListener(this);
        btnViewAll.setOnClickListener(this);

        db = openOrCreateDatabase("ClassDB", Context.MODE_PRIVATE, null);
        db.execSQL("CREATE TABLE IF NOT EXISTS class (classno VARCHAR);");

    }

    @Override
    public void onClick(View view) {

        if (view == btnAdd) {

            if (editClassno.getText().toString().trim().length() == 0)

            {

                showMessage("Error", "Enter a Class No please");
                return;
            }

            db.execSQL("INSERT INTO class VALUES('" + editClassno.getText()
                    + "');");
            showMessage("Success", "Record added");
            clearText();
        }

        if (view == btnDelete) {
            if (editClassno.getText().toString().trim().length() == 0) {
                showMessage("Error", "Please enter Classno");
                return;
            }
            Cursor c = db.rawQuery("SELECT * FROM class WHERE classno='"
                    + editClassno.getText() + "'", null);
            if (c.moveToFirst()) {
                db.execSQL("DELETE FROM class WHERE classno='"
                        + editClassno.getText() + "'");
                showMessage("Success", "Record Deleted");
            } else {
                showMessage("Error", "Invalid Classno");
            }
            clearText();
        }

        if (view == btnModify) {
            if (editClassno.getText().toString().trim().length() == 0) {
                showMessage("Error", "Please enter Classno");
                return;
            }
            Cursor c = db.rawQuery("SELECT * FROM class WHERE classno='"
                    + editClassno.getText() + "'", null);

            if (c.moveToFirst()) {
                db.execSQL("UPDATE class SET class WHERE classno='"
                        + editClassno.getText() + "'");
                showMessage("Success", "Record Modified");

            } else {
                showMessage("Error", "Invalid Clasno");
            }
            clearText();
        }

        if (view == btnViewAll) {
            Cursor c = db.rawQuery("SELECT * FROM class", null);
            if (c.getCount() == 0) {
                showMessage("Error", "No records found");
                return;
            }
            StringBuffer buffer = new StringBuffer();
            while (c.moveToNext()) {
                buffer.append("Classno: " + c.getString(0) + "\n");
                ;
            }
            showMessage("Classes No.", buffer.toString());
        }

    }

    public void clearText() {
        editClassno.setText("");

        editClassno.requestFocus();
    }

    public void showMessage(String title, String message) {
        Builder builder = new Builder(this);
        builder.setCancelable(true);
        builder.setTitle(title);
        builder.setMessage(message);
        builder.show();
    }
}

我的xml

<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/myLayout2"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:stretchColumns="0" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_x="110dp"
        android:layout_y="10dp"
        android:text="Class Section" />

    <Button
        android:id="@+id/btnAdd"
        android:layout_width="100dp"
        android:layout_height="40dp"
        android:layout_x="30dp"
        android:layout_y="200dp"
        android:text="@string/add" />

    <Button
        android:id="@+id/btnDelete"
        android:layout_width="100dp"
        android:layout_height="40dp"
        android:layout_x="150dp"
        android:layout_y="200dp"
        android:text="@string/delete" />

    <Button
        android:id="@+id/btnModify"
        android:layout_width="100dp"
        android:layout_height="40dp"
        android:layout_x="30dp"
        android:layout_y="250dp"
        android:text="@string/modify" />

    <Button
        android:id="@+id/btnViewAll"
        android:layout_width="100dp"
        android:layout_height="40dp"
        android:layout_x="30dp"
        android:layout_y="300dp"
        android:text="@string/view_all" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_x="30dp"
        android:layout_y="102dp"
        android:text="Class_no" />

    <EditText
        android:id="@+id/editClassno"
        android:layout_width="150dp"
        android:layout_height="40dp"
        android:layout_x="120dp"
        android:layout_y="93dp"
        android:ems="10"
        android:inputType="number" />

</AbsoluteLayout>

android manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.e_attendance"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="16"
        android:targetSdkVersion="16" />
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
- 
        <activity
            android:name="com.e_attendance.HomeActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".SignUPActivity" />
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="com.e_attendance.STARTINGPOINT" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Menu"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="com.e_attendance.MENU" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
        <activity
            android:name=".OpenNotes"
            android:label="@string/app_name" >
        </activity>
        <activity android:name=".NewText" >
        </activity>

        <activity
            android:name=".ManageClass"
            android:label="@string/app_name" >
        </activity>

        <activity
            android:name=".ManageStudents"
            android:label="@string/app_name" >
        </activity>

    </application>

</manifest>

Answer 1

您在IDs方法的所有按钮上找不到onCreate()。所以就这么做吧。

  Button btnAdd, btnDelete, btnModify, btnViewAll;

  btnAdd = (Button) findViewById(R.id.btnAdd);
  btnDelete = (Button) findViewById(R.id.btnDelete);
  btnModify = (Button) findViewById(R.id.btnModify);
  btnViewAll = (Button) findViewById(R.id.btnViewAll);

Answer 2

请尝试这种方式，希望这有助于您解决问题。

  @Override
  public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.classdetail);

        editClassno = (EditText) findViewById(R.id.editClassno);
        btnAdd = (Button) findViewById(R.id.btnAdd);
        btnDelete = (Button) findViewById(R.id.btnDelete);
        btnModify = (Button) findViewById(R.id.btnModify);
        btnViewAll = (Button) findViewById(R.id.btnViewAll);
        btnAdd.setOnClickListener(this);
        btnDelete.setOnClickListener(this);
        btnModify.setOnClickListener(this);
        btnViewAll.setOnClickListener(this);

        db = openOrCreateDatabase("ClassDB", Context.MODE_PRIVATE, null);
        db.execSQL("CREATE TABLE IF NOT EXISTS class (classno VARCHAR);");
   }

Answer 3

您需要使用R类创建从Java到XML的桥接，如下所示：

 @Override
public void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.classdetail);

    editClassno = (EditText) findViewById(R.id.editClassno);
    btnAdd = (Button)findViewById(R.id.btnAdd);
    btnDelete= (Button)findViewById(R.id.btnDelete);
    btnModify= (Button)findViewById(R.id.btnModify);
    btnViewAll= (Button)findViewById(R.id.btnViewAll);
    btnAdd.setOnClickListener(this);
    btnDelete.setOnClickListener(this);
    btnModify.setOnClickListener(this);
    btnViewAll.setOnClickListener(this);

    db = openOrCreateDatabase("ClassDB", Context.MODE_PRIVATE, null);
    db.execSQL("CREATE TABLE IF NOT EXISTS class (classno VARCHAR);");

希望这很好用

不幸的是，“App Name”已停止。（Android模拟器，Eclipse）

3 个答案:

不幸的是，“App Name”已停止。 （Android模拟器，Eclipse）

3 个答案:

不幸的是，“App Name”已停止。（Android模拟器，Eclipse）