Question

package com.example.android.login;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    EditText ed1;
    EditText ed2;

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

        ed1 = (EditText) findViewById(R.id.ID);
        ed2 = (EditText) findViewById(R.id.password);

        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(ed1.getText().toString().equals("xyz") &&
                        ed2.getText().toString().equals("abcd")) {

                        Intent intent = new Intent(MainActivity.this, 
                                                  HomePageActivity.class);
                        startActivity(intent);
                }
                else
                    Toast.makeText(getBaseContext(), "Invalid username or password", Toast.LENGTH_LONG).show();
             }
        });
    }
}

这是我的主要活动。如果用户名或密码正确，我想转到HomePageActivity。但是当我这样做时，我的应用程序崩溃了。 HomePageActivity只有onCreate方法，它具有另一个xml文件的setViewContent。

Answer 1

试试这个例子：

1）LoginActivity.class：----------

public class LoginActivity extends AppCompatActivity {

private EditText edt_1;
private EditText edt_2;
private Button b;
private final String EDT1 = "xyz";
private final String EDT2 = "abcd";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.login_activity);

    edt_1 = (EditText) findViewById(R.id.edt_1);
    edt_2 = (EditText) findViewById(R.id.edt_2);
    b = (Button) findViewById(R.id.b);
    b.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(!edt_1.getText().toString().isEmpty() && !edt_2.getText().toString().isEmpty()){
                if(edt_1.getText().toString().equals(EDT1) && edt_2.getText().toString().equals(EDT2)){
                    finish();
                    Intent information_intent = new Intent(LoginActivity.this, MainActivity.class);
                    startActivity(information_intent);
                }else{
                    Toast.makeText(getApplicationContext() , "Wrong" , Toast.LENGTH_LONG).show();
                }
            }else{
                Toast.makeText(getApplicationContext() , "Edt 1 or Edt 2 is empty"  , Toast.LENGTH_LONG).show();
            }
        }
    });

}

}

2）MainActivity.class：------------

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_activity);
}

}

3）login_activity.xml：----

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">

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

<TextView
    android:layout_width="70dp"
    android:layout_height="wrap_content"
    android:layout_marginStart="10dp"
    android:id="@+id/tv1"
    android:layout_centerVertical="true"
    android:layout_alignParentStart="true"
    android:text="Edt 1"/>

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:hint="Enter 1..."
    android:layout_alignParentEnd="true"
    android:layout_toEndOf="@id/tv1"
    android:layout_centerVertical="true"
    android:layout_marginStart="20dp"
    android:background="@android:color/transparent"
    android:id="@+id/edt_1"
    android:text=""/>

</RelativeLayout>

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

    <TextView
        android:layout_width="70dp"
        android:layout_height="wrap_content"
        android:id="@+id/tv2"
        android:layout_marginStart="10dp"
        android:layout_centerVertical="true"
        android:layout_alignParentStart="true"
        android:text="Edt 2"/>

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="Enter 2..."
        android:id="@+id/edt_2"
        android:layout_alignParentEnd="true"
        android:layout_toEndOf="@id/tv2"
        android:layout_centerVertical="true"
        android:layout_marginStart="20dp"
        android:background="@android:color/transparent"
        android:text=""/>

</RelativeLayout>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:id="@+id/b"
    android:layout_marginTop="50dp"
    android:text="Check"/>

</LinearLayout>

4）main_activity.xml：-------

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center">

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

</LinearLayout>

5）AndroidManifest：

<activity android:name="com.example.admin.accessories.MainActivity">
        <intent-filter>
            <action android:name="com.example.admin.accessories.MainActivity" />

            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>

<activity android:name="com.example.admin.accessories.LoginActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

Answer 2

删除toString（）

以更改条件

if(ed1.getText().equals("xyz") && ed2.getText().equals("abcd"))

另外，对于你的吐司，最好使用

getApplicationContext()

当我写正确的用户名和密码时，我的应用程序崩溃了

2 个答案: