java - Android 数据库应用程序在“运行到电话”中崩溃

Question

我是 Android 数据库新手。我正在按照有关数据库的 YouTube 教程创建一个应用程序 ( youtube )。

我遵循了一切，当我运行应用程序时，发生了一些事情，应用程序崩溃了。

当我首先运行应用程序时，一切正常，但当我开始单击“创建”按钮时，应用程序崩溃了。

这是错误:

12-11 23:17:54.164: E/AndroidRuntime(30226): FATAL EXCEPTION: main
12-11 23:17:54.164: E/AndroidRuntime(30226): java.lang.IllegalStateException: Could not find a method Adddata(View) in the activity class com.example.studentdatabase.MainActivity for onClick handler on view class android.widget.Button with id 'button1'
12-11 23:17:54.164: E/AndroidRuntime(30226):    at android.view.View$1.onClick(View.java:3594)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at android.view.View.performClick(View.java:4212)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at android.view.View$PerformClick.run(View.java:17476)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at android.os.Handler.handleCallback(Handler.java:800)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at android.os.Handler.dispatchMessage(Handler.java:100)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at android.os.Looper.loop(Looper.java:194)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at android.app.ActivityThread.main(ActivityThread.java:5371)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at java.lang.reflect.Method.invokeNative(Native Method)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at java.lang.reflect.Method.invoke(Method.java:525)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at dalvik.system.NativeStart.main(Native Method)
12-11 23:17:54.164: E/AndroidRuntime(30226): Caused by: java.lang.NoSuchMethodException: Adddata [class android.view.View]
12-11 23:17:54.164: E/AndroidRuntime(30226):    at java.lang.Class.getConstructorOrMethod(Class.java:460)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at java.lang.Class.getMethod(Class.java:915)
12-11 23:17:54.164: E/AndroidRuntime(30226):    at android.view.View$1.onClick(View.java:3587)
12-11 23:17:54.164: E/AndroidRuntime(30226):    ... 11 more

我的代码也在这里: 来自主要 Activity

   package com.example.studentdatabase;


import android.os.Bundle;
import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.graphics.Color;
import android.graphics.Typeface;
import android.view.View;
import android.widget.EditText;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;

public class MainActivity extends Activity {
    String fname,lname,email;
    SQLiteDatabase db;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        db= openOrCreateDatabase("MyDB1",MODE_PRIVATE,null);
        db.execSQL("CREATE TABLE IF NOT EXISTS Student(fname VARCHAR,lname VARCHAR,email VARCHAR)");
    }

        private void Adddata(View view){

        EditText editText1=(EditText) findViewById(R.id.firstname);
        EditText editText2=(EditText) findViewById(R.id.lastname);
        EditText editText3=(EditText) findViewById(R.id.email);

        fname=editText1.getText().toString();
        lname=editText2.getText().toString();
        email=editText3.getText().toString();
        db.execSQL("INSERT INTO Student VALUES('"+fname+"','"+lname+"','"+email+"')");


    }   

    private void showdata(View view){

        Cursor c=db.rawQuery("SELECT * from Student", null);
        int count=c.getCount();
        c.moveToFirst();
        TableLayout tableLayout=new TableLayout(getApplicationContext());
        tableLayout.setVerticalScrollBarEnabled(true);
        TableRow tableRow;
        TextView textView,textView1,textView2,textView3,textView4,textView5;
        tableRow=new TableRow(getApplicationContext());

        textView=new TextView(getApplicationContext());
        textView.setText("Firstname");
        textView.setTextColor(Color.RED);
        textView.setTypeface(null,Typeface.BOLD);
        textView.setPadding(20, 20, 20, 20);
        tableRow.addView(textView);

        textView4=new TextView(getApplicationContext());
        textView4.setText("LastName");
        textView4.setTextColor(Color.RED);
        textView4.setTypeface(null,Typeface.BOLD);
        textView4.setPadding(20, 20, 20, 20);

        textView5=new TextView(getApplicationContext());
        textView5.setText("LastName");
        textView5.setTextColor(Color.RED);
        textView5.setTypeface(null,Typeface.BOLD);
        textView5.setPadding(20, 20, 20, 20);
        tableRow.addView(tableRow);

        for(Integer j=0; j < count; j++){
            tableRow=new TableRow(getApplicationContext());
            textView1=new TextView(getApplicationContext());
            textView1.setText(c.getString(c.getColumnIndex("fname")));
            textView2=new TextView(getApplicationContext());
            textView2.setText(c.getString(c.getColumnIndex("lname")));
            textView3=new TextView(getApplicationContext());
            textView3.setText(c.getString(c.getColumnIndex("email")));

            textView1.setPadding(20, 20,20, 20);
            textView2.setPadding(20, 20,20, 20);
            textView3.setPadding(20, 20,20, 20);

            tableRow.addView(textView1);
            tableRow.addView(textView2);
            tableRow.addView(textView3);

            tableLayout.addView(tableRow);
            c.moveToNext();




        }
        setContentView(tableLayout);
        db.close();
        }
        public void close(View view){

            System.exit(0);
        }




}

我的activity_main.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView2"
        android:layout_below="@+id/textView2"
        android:layout_marginTop="25dp"
        android:text="last Name" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="25dp"
        android:text="Email" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="18dp"
        android:layout_marginTop="27dp"
        android:text="First Name" />

    <EditText
        android:id="@+id/firstname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView2"
        android:layout_alignBottom="@+id/textView2"
        android:layout_toRightOf="@+id/textView2"
        android:ems="10" >

        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/lastname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView1"
        android:layout_alignBottom="@+id/textView1"
        android:layout_alignLeft="@+id/firstname"
        android:ems="10" />

    <EditText
        android:id="@+id/email"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView3"
        android:layout_alignBottom="@+id/textView3"
        android:layout_toRightOf="@+id/textView1"
        android:ems="10" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView3"
        android:layout_below="@+id/email"
        android:layout_marginTop="28dp"
        android:onClick="Adddata"
        android:text="create" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/button1"
        android:layout_alignBottom="@+id/button1"
        android:layout_alignRight="@+id/email"
        android:layout_marginRight="42dp"
        android:onClick="showdata"
        android:text="Show Table" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button1"
        android:layout_below="@+id/button1"
        android:layout_marginTop="33dp"
        android:onClick="close"
        android:text="Close" />

</RelativeLayout>

Answer 1

方法 AddData 必须是公共(public)的，并接受 View 作为其唯一参数。

引用号:http://developer.android.com/reference/android/widget/Button.html