所以我需要我的简单应用才能拥有密码。默认密码为“admin”，如果用户愿意，用户可以更改密码。但我在改变部分时遇到了问题。我不知道为什么，但我为此做的活动总是强制关闭。这是我第一次使用SharedPreferences。我不知道我是否正确使用过它。请帮我。这是我的代码：
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class ChangePass extends Activity {
@SuppressLint("CommitPrefEdits")
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.change_pass);
final SharedPreferences settings = ChangePass.this.getSharedPreferences("pass", 0);
final SharedPreferences.Editor editor = settings.edit();
final EditText CurPass;
final EditText NewPass1;
final EditText NewPass2;
Button BtnSubmit;
final TextView errorMsg;
CurPass = (EditText)this.findViewById(R.id.curPW);
NewPass1 = (EditText)this.findViewById(R.id.newPW1);
NewPass2 = (EditText)this.findViewById(R.id.newPW2);
BtnSubmit = (Button)this.findViewById(R.id.btnSubmit);
errorMsg = (Button)this.findViewById(R.id.errorTxt);
BtnSubmit.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
String current = CurPass.getText().toString().trim();
String new1 = NewPass1.getText().toString().trim();
String new2 = NewPass2.getText().toString().trim();
String CurrentPW = settings.getString("Password", "admin");
if (CurrentPW.equals(current)) {
if (new1.equals(new2)) {
editor.putString("Password", new1).apply();
Toast.makeText(getApplicationContext(), "Password successfully changed!",
Toast.LENGTH_LONG).show();
CurPass.setText("");
NewPass1.setText("");
NewPass2.setText("");
}
else {
errorMsg.setText("ERROR: Passwords did not match.");
}
}
else {
errorMsg.setText("ERROR: Wrong password.");
}
}
});
}
XML：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/new_bg_pass" >
<EditText
android:id="@+id/curPW"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="144dp"
android:ems="10"
android:inputType="textPassword" >
<requestFocus />
</EditText>
<EditText
android:id="@+id/newPW1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/curPW"
android:layout_centerHorizontal="true"
android:layout_marginTop="57dp"
android:ems="10"
android:inputType="textPassword" />
<TextView
android:id="@+id/TextView01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/newPW1"
android:layout_alignLeft="@+id/textView1"
android:text="New Password:"
android:textAppearance="?android:attr/textAppearanceMedium" />
<EditText
android:id="@+id/newPW2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/newPW1"
android:layout_below="@+id/newPW1"
android:layout_marginTop="35dp"
android:ems="10"
android:inputType="textPassword" />
<TextView
android:id="@+id/TextView02"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/newPW2"
android:layout_alignLeft="@+id/TextView01"
android:text="Retype New Password:"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/newPW1"
android:layout_marginRight="57dp"
android:layout_toLeftOf="@+id/curPW"
android:text="Current Password:"
android:textAppearance="?android:attr/textAppearanceMedium" />
<Button
android:id="@+id/btnSubmit"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/newPW2"
android:layout_centerHorizontal="true"
android:layout_marginTop="40dp"
android:text="Submit" />
<TextView
android:id="@+id/errorTxt"
android:layout_width="400dp"
android:layout_height="wrap_content"
android:layout_above="@+id/textView1"
android:layout_centerHorizontal="true"
android:layout_marginBottom="34dp"
android:text=""
android:textAppearance="?android:attr/textAppearanceLarge"
android:textColor="#FF0000" />
</RelativeLayout>
这是来自LogCat：
02-20 12:28:58.156: E/AndroidRuntime(338): FATAL EXCEPTION: main
02-20 12:28:58.156: E/AndroidRuntime(338): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.login/com.login.ChangePass}: java.lang.ClassCastException: android.widget.TextView
02-20 12:28:58.156: E/AndroidRuntime(338): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
02-20 12:28:58.156: E/AndroidRuntime(338): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
02-20 12:28:58.156: E/AndroidRuntime(338): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
02-20 12:28:58.156: E/AndroidRuntime(338): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
02-20 12:28:58.156: E/AndroidRuntime(338): at android.os.Handler.dispatchMessage(Handler.java:99)
02-20 12:28:58.156: E/AndroidRuntime(338): at android.os.Looper.loop(Looper.java:123)
02-20 12:28:58.156: E/AndroidRuntime(338): at android.app.ActivityThread.main(ActivityThread.java:3683)
02-20 12:28:58.156: E/AndroidRuntime(338): at java.lang.reflect.Method.invokeNative(Native Method)
02-20 12:28:58.156: E/AndroidRuntime(338): at java.lang.reflect.Method.invoke(Method.java:507)
02-20 12:28:58.156: E/AndroidRuntime(338): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
02-20 12:28:58.156: E/AndroidRuntime(338): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-20 12:28:58.156: E/AndroidRuntime(338): at dalvik.system.NativeStart.main(Native Method)
02-20 12:28:58.156: E/AndroidRuntime(338): Caused by: java.lang.ClassCastException: android.widget.TextView
02-20 12:28:58.156: E/AndroidRuntime(338): at com.login.ChangePass.onCreate(ChangePass.java:35)
02-20 12:28:58.156: E/AndroidRuntime(338): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
02-20 12:28:58.156: E/AndroidRuntime(338): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
02-20 12:28:58.156: E/AndroidRuntime(338): ... 11 more
答案 0 :(得分：1)
您已将TextView定义为
final TextView errorMsg;
你正试图把它投入按钮：
errorMsg = (Button)this.findViewById(R.id.errorTxt);
此外你应该按如下方式进行投射：
errorMsg = (TextView)this.findViewById(R.id.errorTxt);
<强>编辑：
创建共享偏好：
SharedPreferences sp=getSharedPreferences("Login", 0);
SharedPreferences.Editor Ed=sp.edit();
Ed.putString("Psw",Value);
Ed.commit();
从共享偏好中获取价值：
SharedPreferences sp1=this.getSharedPreferences("Login",null);
String pass = sp1.getString("Psw", null);
更新共享首选项值：
if (pass.equals(current)) {
Ed.putString("Psw", new1);
Ed.commit();
}
答案 1 :(得分：0)
清单可能有一些问题，看起来应该更像：
<activity android:name=".start" 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= ".Main">
</activity>