如何在 Android 中实现 PDF 选择器？

在本文中，我们将了解如何在 android studio 中实现 PDF 选择器并获取 pdf 的 Uri 和 Path。在这个应用程序中，我们将获得用户读取外部存储的权限，然后向用户显示所选 PDF 的 Uri 和路径，表明我们已成功选择 PDF。这是我们将在此应用程序中构建的示例视频。请注意，我们将使用Java语言来实现这个应用程序。

分步实施

第 1 步：创建一个新项目

• 打开一个新项目。
• 我们将使用Java语言开发 Empty Activity。保持所有其他选项不变。
• 您可以在方便时更改项目的名称。
• 将有两个名为 activity_main.xml 和 MainActivity 的默认文件。Java

如果您不知道如何在 Android Studio 中创建新项目，可以参考如何在 Android Studio 中创建/启动新项目？

第二步：添加存储权限

按照路径app > manifests > AndroidManifest.xml并将以下代码粘贴到其中。

第 3 步：处理 XML 文件

导航到app > res > layout > activity_main.xml并将以下代码添加到该文件。下面是activity_main.xml文件的代码。

第 4 步：处理Java文件

转到MainActivity。 Java文件并参考以下代码。下面是 MainActivity 的代码。 Java文件。代码内部添加注释以更详细地理解代码

Java

package com.example.pdfpicker;
  
import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Bundle;
import android.text.Html;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import androidx.activity.result.ActivityResult;
import androidx.activity.result.ActivityResultCallback;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
  
public class MainActivity extends AppCompatActivity {
  
    // Initialize variable
    Button btSelect;
    TextView tvUri, tvPath;
    ActivityResultLauncher resultLauncher;
  
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
  
        // assign variable
        btSelect = findViewById(R.id.bt_select);
        tvUri = findViewById(R.id.tv_uri);
        tvPath = findViewById(R.id.tv_path);
  
        // Initialize result launcher
        resultLauncher = registerForActivityResult(
            new ActivityResultContracts
                .StartActivityForResult(),
            new ActivityResultCallback() {
                @Override
                public void onActivityResult(
                    ActivityResult result)
                {
                    // Initialize result data
                    Intent data = result.getData();
                    // check condition
                    if (data != null) {
                        // When data is not equal to empty
                        // Get PDf uri
                        Uri sUri = data.getData();
                        // set Uri on text view
                        tvUri.setText(Html.fromHtml(
                            "PDF Uri
"
                            + sUri));
  
                        // Get PDF path
                        String sPath = sUri.getPath();
                        // Set path on text view
                        tvPath.setText(Html.fromHtml(
                            "PDF Path
"
                            + sPath));
                    }
                }
            });
  
        // Set click listener on button
        btSelect.setOnClickListener(
            new View.OnClickListener() {
                @Override public void onClick(View v)
                {
                    // check condition
                    if (ActivityCompat.checkSelfPermission(
                            MainActivity.this,
                            Manifest.permission
                                .READ_EXTERNAL_STORAGE)
                        != PackageManager
                               .PERMISSION_GRANTED) {
                        // When permission is not granted
                        // Result permission
                        ActivityCompat.requestPermissions(
                            MainActivity.this,
                            new String[] {
                                Manifest.permission
                                    .READ_EXTERNAL_STORAGE },
                            1);
                    }
                    else {
                        // When permission is granted
                        // Create method
                        selectPDF();
                    }
                }
            });
    }
  
    private void selectPDF()
    {
        // Initialize intent
        Intent intent
            = new Intent(Intent.ACTION_GET_CONTENT);
        // set type
        intent.setType("application/pdf");
        // Launch intent
        resultLauncher.launch(intent);
    }
  
    @Override
    public void onRequestPermissionsResult(
        int requestCode, @NonNull String[] permissions,
        @NonNull int[] grantResults)
    {
        super.onRequestPermissionsResult(
            requestCode, permissions, grantResults);
  
        // check condition
        if (requestCode == 1 && grantResults.length > 0
            && grantResults[0]
                   == PackageManager.PERMISSION_GRANTED) {
            // When permission is granted
            // Call method
            selectPDF();
        }
        else {
            // When permission is denied
            // Display toast
            Toast
                .makeText(getApplicationContext(),
                          "Permission Denied",
                          Toast.LENGTH_SHORT)
                .show();
        }
    }
}

这是我们应用程序的最终输出。

输出：