Android Java页面开发需求：输入数字点击按钮跳转对应PDF链接

Here's a step-by-step implementation to meet your requirements:

1. Layout File (res/layout/activity_main.xml) #

First, create the UI with an EditText for number input and a Button to trigger the PDF redirect:

<?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"
    android:padding="16dp"
    android:gravity="center">

    <EditText
        android:id="@+id/input_number"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="Enter 1 or 2"
        android:inputType="number"
        android:textSize="18sp"/>

    <Button
        android:id="@+id/open_pdf_btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Open PDF"
        android:layout_marginTop="20dp"/>

</LinearLayout>

2. Activity Logic (MainActivity.java) #

Implement the click listener to validate input and launch the appropriate PDF link:

import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private EditText inputNumber;
    private Button openPdfBtn;

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

        inputNumber = findViewById(R.id.input_number);
        openPdfBtn = findViewById(R.id.open_pdf_btn);

        openPdfBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String input = inputNumber.getText().toString().trim();
                
                // Validate input
                if (input.isEmpty()) {
                    Toast.makeText(MainActivity.this, "Please enter a number", Toast.LENGTH_SHORT).show();
                    return;
                }

                String pdfUrl;
                switch (input) {
                    case "1":
                        pdfUrl = "https://www.mywebsite/myfile1.pdf";
                        break;
                    case "2":
                        pdfUrl = "https://www.mywebsite/myfile2.pdf";
                        break;
                    default:
                        Toast.makeText(MainActivity.this, "Please enter 1 or 2", Toast.LENGTH_SHORT).show();
                        return;
                }

                // Create intent to open PDF
                Intent intent = new Intent(Intent.ACTION_VIEW);
                intent.setDataAndType(Uri.parse(pdfUrl), "application/pdf");
                
                // Check if there's an app to handle the intent
                if (intent.resolveActivity(getPackageManager()) != null) {
                    startActivity(intent);
                } else {
                    Toast.makeText(MainActivity.this, "No PDF viewer app found", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }
}

3. Update AndroidManifest.xml #

Add the INTERNET permission since we're accessing online PDFs, and ensure your activity is registered:

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

    <!-- Required for accessing online PDFs -->
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>

</manifest>

Key Notes: #

• Input Validation: The code checks for empty input and valid numbers (1 or 2), showing toast messages for invalid cases.
• PDF Opening: The intent uses ACTION_VIEW with the PDF URL. It first checks if there's a compatible app (like a PDF viewer or browser) to handle the request, preventing crashes if no app is available.
• HTTPS: Ensure your PDF links use https instead of http to comply with Android's cleartext traffic policies (for API level 28+).

内容的提问来源于stack exchange，提问作者sam