我遇到了一个问题，onclick 找不到它应该执行的方法。Android 尝试调用 onClick 方法public void fahrplan(View v,Connection conn) 但找不到它。我的代码的详细信息如下，错误是在那之后。请帮我确定为什么android找不到onClick方法。谢谢。
现在只有一个活动，所以没有其他代码在运行。
MainActivity.java
package eu.rathenau.fahrgemeinschaft;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class MainActivity extends AppCompatActivity {
String x;
TextView testTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
testTextView =(TextView)findViewById(R.id.textView);
connect();
}
public Connection connect() {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://"ip-address"/MarcelGerber?user="username"&password="password");
return conn;
} catch (Exception e) {
return null;
}
}
public String getAllKürzel(Connection conn) {
if (conn == null) {
return null;
}
Statement st = null;
ResultSet rs = null;
try {
st = conn.createStatement();
rs = st.executeQuery("SELECT Kürzel FROM Benutzer");
int length = 0;
if (rs.last()) {
length = rs.getRow();
rs.beforeFirst();
}
String[] kürzel = new String[length];
while(rs.next()) {
kürzel[rs.getRow() - 1] = rs.getString("Kürzel");
}
x=kürzel[1];
return x;
} catch (Exception e) {
return null;
} finally {
if (rs != null) {
try {
rs.close();
} catch (Exception e) {
}
}
if (st != null) {
try {
st.close();
} catch (Exception e) {
}
}
}
}
public void fahrplan (View v,Connection conn){
testTextView.setText(getAllKürzel(conn));
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<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="eu.rathenau.fahrgemeinschaft.MainActivity">
<Button
android:layout_width="match_parent"
android:layout_height="70dp"
android:text="@string/fahrplan"
android:id="@+id/buttonFahrplan"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:onClick="fahrplan"/>
<TextView
android:layout_width="match_parent"
android:layout_height="70dp"
android:text="hallo"
android:id="@+id/textView"
android:layout_below="@+id/buttonFahrplan"
android:layout_centerHorizontal="true"
android:layout_marginTop="66dp" />
</RelativeLayout>
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="eu.rathenau.fahrgemeinschaft">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity"
android:screenOrientation="portrait">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
日志
04-22 11:20:39.830 28066-28066/eu.rathenau.fahrgemeinschaft E/AndroidRuntime: FATAL EXCEPTION: main
Process: eu.rathenau.fahrgemeinschaft, PID: 28066
java.lang.IllegalStateException: Could not find method fahrplan(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.support.v7.widget.AppCompatButton with id 'buttonFahrplan'
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.resolveMethod(AppCompatViewInflater.java:321)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:280)
at android.view.View.performClick(View.java:4856)
at android.view.View$PerformClick.run(View.java:19956)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:211)
at android.app.ActivityThread.main(ActivityThread.java:5373)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1020)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815)
如果你能帮助我，那就太好了。