1、在res目錄下新建一個(gè)xml目錄滨嘱，里面新建一個(gè)名為file_paths的xml文件峰鄙，文件內(nèi)容如下：

<?xml version="1.0" encoding="utf-8"?>
<resources >
    <paths>
        <external-path path="" name="download"/>
        <external-path name="external_files" path="."/>
        <!--1、對(duì)應(yīng)內(nèi)部?jī)?nèi)存卡根目錄：Context.getFileDir()-->
        <files-path
            name="int_root"
            path="/" />
        <!--2太雨、對(duì)應(yīng)應(yīng)用默認(rèn)緩存根目錄：Context.getCacheDir()-->
        <cache-path
            name="app_cache"
            path="/" />
        <!--3吟榴、對(duì)應(yīng)外部?jī)?nèi)存卡根目錄：Environment.getExternalStorageDirectory()-->
        <external-path
            name="ext_root"
            path="pictures/" />
        <!--4、對(duì)應(yīng)外部?jī)?nèi)存卡根目錄下的APP公共目錄：Context.getExternalFileDir(String)-->
        <external-files-path
            name="ext_pub"
            path="/" />
        <!--5囊扳、對(duì)應(yīng)外部?jī)?nèi)存卡根目錄下的APP緩存目錄：Context.getExternalCacheDir()-->
        <external-cache-path
            name="ext_cache"
            path="/" />
    </paths>
</resources>

2吩翻、在androidMainfast里添加

        <provider
            android:name="androidx.core.content.FileProvider"
            android:authorities="com.example.viewpaerdemo.provider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths" />
        </provider>

android:authorities="com.example.viewpaerdemo.provider"這里是包名.provider。
3.添加權(quán)限
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
4锥咸、activity里的打開代碼：

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
//            加入此代碼狭瞎，解決FileUriExposedException問題
           if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.N) {
               StrictMode.VmPolicy.Builder builder = new StrictMode.VmPolicy.Builder();
               StrictMode.setVmPolicy(builder.build());
               builder.detectFileUriExposure();
//               builder.detectAll();刪除檢測(cè)APK中調(diào)試代碼是否暴露敏感信息
}
        }
    public void openPdf() {
        String path1 = Environment.getExternalStorageDirectory().getPath();
        File file = new File(path1 + "/", "**.pdf");
        Intent intent = new Intent("android.intent.action.VIEW");
        intent.addCategory("android.intent.category.DEFAULT");
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        Uri uri;
        if(Build.VERSION.PREVIEW_SDK_INT>=Build.VERSION_CODES.N){
            //通過fileProvider創(chuàng)建一個(gè)content類型的uri
            uri=FileProvider.getUriForFile(this,"com.example.viewpaerdemo.provider",file);
            intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        }else {
            uri=Uri.fromFile(file);
        }
        intent.setDataAndType(uri,"application/pdf");
        if(file.exists()) {
            this.startActivity(intent);
        }
    }

他會(huì)使用你手機(jī)中存在的閱讀器打開，完結(jié)搏予。