Android 開發之 Webview 上傳圖片代碼（Kotlin版）

可以直接滑動到頁面底部複製可以正常編譯運行的 Kotlin 代碼。

我們一個新的 Android 項目是用 Kotlin 來開發，因使用到了 Webview，不可避免地會遇到 Webview 中上傳圖片的問題，如果不做處理的話，在 web 中點擊是沒有任何反應的，需要寫一堆方法。

我直接拿這篇文章「Android WebView那些坑之上傳文件」的 Java 代碼，然後用 Android Studio的自動轉換，轉換爲 Kotlin 代碼，但有兩處報錯。

首先把 Java 代碼貼出來：

public class MainActivity extends AppCompatActivity {

    private ValueCallback<Uri> uploadMessage;
    private ValueCallback<Uri[]> uploadMessageAboveL;
    private final static int FILE_CHOOSER_RESULT_CODE = 10000;

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

        WebView webview = (WebView) findViewById(R.id.web_view);
        assert webview != null;
        WebSettings settings = webview.getSettings();
        settings.setUseWideViewPort(true);
        settings.setLoadWithOverviewMode(true);
        settings.setJavaScriptEnabled(true);
        webview.setWebChromeClient(new WebChromeClient() {

            // For Android < 3.0
            public void openFileChooser(ValueCallback<Uri> valueCallback) {
                uploadMessage = valueCallback;
                openImageChooserActivity();
            }

            // For Android  >= 3.0
            public void openFileChooser(ValueCallback valueCallback, String acceptType) {
                uploadMessage = valueCallback;
                openImageChooserActivity();
            }

            //For Android  >= 4.1
            public void openFileChooser(ValueCallback<Uri> valueCallback, String acceptType, String capture) {
                uploadMessage = valueCallback;
                openImageChooserActivity();
            }

            // For Android >= 5.0
            @Override
            public boolean onShowFileChooser(WebView webView, ValueCallback<Uri[]> filePathCallback, WebChromeClient.FileChooserParams fileChooserParams) {
                uploadMessageAboveL = filePathCallback;
                openImageChooserActivity();
                return true;
            }
        });
        String targetUrl = "file:///android_asset/up.html";
        webview.loadUrl(targetUrl);
    }

    private void openImageChooserActivity() {
        Intent i = new Intent(Intent.ACTION_GET_CONTENT);
        i.addCategory(Intent.CATEGORY_OPENABLE);
        i.setType("image/*");
        startActivityForResult(Intent.createChooser(i, "Image Chooser"), FILE_CHOOSER_RESULT_CODE);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == FILE_CHOOSER_RESULT_CODE) {
            if (null == uploadMessage && null == uploadMessageAboveL) return;
            Uri result = data == null || resultCode != RESULT_OK ? null : data.getData();
            if (uploadMessageAboveL != null) {
                onActivityResultAboveL(requestCode, resultCode, data);
            } else if (uploadMessage != null) {
                uploadMessage.onReceiveValue(result);
                uploadMessage = null;
            }
        }
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private void onActivityResultAboveL(int requestCode, int resultCode, Intent intent) {
        if (requestCode != FILE_CHOOSER_RESULT_CODE || uploadMessageAboveL == null)
            return;
        Uri[] results = null;
        if (resultCode == Activity.RESULT_OK) {
            if (intent != null) {
                String dataString = intent.getDataString();
                ClipData clipData = intent.getClipData();
                if (clipData != null) {
                    results = new Uri[clipData.getItemCount()];
                    for (int i = 0; i < clipData.getItemCount(); i++) {
                        ClipData.Item item = clipData.getItemAt(i);
                        results[i] = item.getUri();
                    }
                }
                if (dataString != null)
                    results = new Uri[]{Uri.parse(dataString)};
            }
        }
        uploadMessageAboveL.onReceiveValue(results);
        uploadMessageAboveL = null;
    }
}

轉換後的 Kotlin 代碼：

class MainActivity : AppCompatActivity() {

    private var uploadMessage: ValueCallback<Uri>? = null
    private var uploadMessageAboveL: ValueCallback<Array<Uri>>? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val webview = findViewById(R.id.web_view) as WebView
        val settings = webview.settings
        settings.useWideViewPort = true
        settings.loadWithOverviewMode = true
        settings.javaScriptEnabled = true
        webview.webChromeClient = object : WebChromeClient() {

            // For Android < 3.0
            fun openFileChooser(valueCallback: ValueCallback<Uri>) {
                uploadMessage = valueCallback
                openImageChooserActivity()
            }

            // For Android  >= 3.0
            fun openFileChooser(valueCallback: ValueCallback<*>, acceptType: String) {
                uploadMessage = valueCallback
                openImageChooserActivity()
            }

            //For Android  >= 4.1
            fun openFileChooser(
                valueCallback: ValueCallback<Uri>,
                acceptType: String,
                capture: String
            ) {
                uploadMessage = valueCallback
                openImageChooserActivity()
            }

            // For Android >= 5.0
            override fun onShowFileChooser(
                webView: WebView,
                filePathCallback: ValueCallback<Array<Uri>>,
                fileChooserParams: WebChromeClient.FileChooserParams
            ): Boolean {
                uploadMessageAboveL = filePathCallback
                openImageChooserActivity()
                return true
            }
        }
        val targetUrl = "file:///android_asset/up.html"
        webview.loadUrl(targetUrl)
    }

    private fun openImageChooserActivity() {
        val i = Intent(Intent.ACTION_GET_CONTENT)
        i.addCategory(Intent.CATEGORY_OPENABLE)
        i.type = "image/*"
        startActivityForResult(Intent.createChooser(i, "Image Chooser"), FILE_CHOOSER_RESULT_CODE)
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == FILE_CHOOSER_RESULT_CODE) {
            if (null == uploadMessage && null == uploadMessageAboveL) return
            val result = if (data == null || resultCode != Activity.RESULT_OK) null else data.data
            if (uploadMessageAboveL != null) {
                onActivityResultAboveL(requestCode, resultCode, data)
            } else if (uploadMessage != null) {
                uploadMessage!!.onReceiveValue(result)
                uploadMessage = null
            }
        }
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private fun onActivityResultAboveL(requestCode: Int, resultCode: Int, intent: Intent?) {
        if (requestCode != FILE_CHOOSER_RESULT_CODE || uploadMessageAboveL == null)
            return
        var results: Array<Uri>? = null
        if (resultCode == Activity.RESULT_OK) {
            if (intent != null) {
                val dataString = intent.dataString
                val clipData = intent.clipData
                if (clipData != null) {
                    results = arrayOfNulls(clipData.itemCount)
                    for (i in 0 until clipData.itemCount) {
                        val item = clipData.getItemAt(i)
                        results[i] = item.uri
                    }
                }
                if (dataString != null)
                    results = arrayOf(Uri.parse(dataString))
            }
        }
        uploadMessageAboveL!!.onReceiveValue(results)
        uploadMessageAboveL = null
    }

    companion object {
        private val FILE_CHOOSER_RESULT_CODE = 10000
    }
}

兩處報錯如下。

第 1 處：

修改後：

// For Android  >= 3.0
fun openFileChooser(valueCallback: ValueCallback<Uri>, acceptType: String) {
     uploadMessage = valueCallback
     openImageChooserActivity()
}

第 2 處：

修改後：

@TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private fun onActivityResultAboveL(requestCode: Int, resultCode: Int, intent: Intent?) {
        if (requestCode != FILE_CHOOSER_RESULT_CODE || uploadMessageAboveL == null)
            return
        var results: Array<Uri>? = null
        if (resultCode == Activity.RESULT_OK) {
            if (intent != null) {
                val dataString = intent.dataString
                val clipData = intent.clipData
                if (clipData != null) {
                    results = Array(clipData.itemCount){
                        i -> clipData.getItemAt(i).uri
                    }
                }
                if (dataString != null)
                    results = arrayOf(Uri.parse(dataString))
            }
        }
        uploadMessageAboveL!!.onReceiveValue(results)
        uploadMessageAboveL = null
    }

修改後就可以正常編譯運行了。

最後把完整的 Kotlin 代碼貼上來：

class MainActivity : AppCompatActivity() {

    private var uploadMessage: ValueCallback<Uri>? = null
    private var uploadMessageAboveL: ValueCallback<Array<Uri>>? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val webview = findViewById(R.id.web_view) as WebView
        val settings = webview.settings
        settings.useWideViewPort = true
        settings.loadWithOverviewMode = true
        settings.javaScriptEnabled = true
        webview.webChromeClient = object : WebChromeClient() {

            // For Android < 3.0
            fun openFileChooser(valueCallback: ValueCallback<Uri>) {
                uploadMessage = valueCallback
                openImageChooserActivity()
            }

            // For Android  >= 3.0
            fun openFileChooser(valueCallback: ValueCallback<Uri>, acceptType: String) {
                uploadMessage = valueCallback
                openImageChooserActivity()
            }

            //For Android  >= 4.1
            fun openFileChooser(
                valueCallback: ValueCallback<Uri>,
                acceptType: String,
                capture: String
            ) {
                uploadMessage = valueCallback
                openImageChooserActivity()
            }

            // For Android >= 5.0
            override fun onShowFileChooser(
                webView: WebView,
                filePathCallback: ValueCallback<Array<Uri>>,
                fileChooserParams: WebChromeClient.FileChooserParams
            ): Boolean {
                uploadMessageAboveL = filePathCallback
                openImageChooserActivity()
                return true
            }
        }
        val targetUrl = "file:///android_asset/up.html"
        webview.loadUrl(targetUrl)
    }

    private fun openImageChooserActivity() {
        val i = Intent(Intent.ACTION_GET_CONTENT)
        i.addCategory(Intent.CATEGORY_OPENABLE)
        i.type = "image/*"
        startActivityForResult(Intent.createChooser(i, "Image Chooser"), FILE_CHOOSER_RESULT_CODE)
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == FILE_CHOOSER_RESULT_CODE) {
            if (null == uploadMessage && null == uploadMessageAboveL) return
            val result = if (data == null || resultCode != Activity.RESULT_OK) null else data.data
            if (uploadMessageAboveL != null) {
                onActivityResultAboveL(requestCode, resultCode, data)
            } else if (uploadMessage != null) {
                uploadMessage!!.onReceiveValue(result)
                uploadMessage = null
            }
        }
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private fun onActivityResultAboveL(requestCode: Int, resultCode: Int, intent: Intent?) {
        if (requestCode != FILE_CHOOSER_RESULT_CODE || uploadMessageAboveL == null)
            return
        var results: Array<Uri>? = null
        if (resultCode == Activity.RESULT_OK) {
            if (intent != null) {
                val dataString = intent.dataString
                val clipData = intent.clipData
                if (clipData != null) {
                    results = Array(clipData.itemCount){
                        i -> clipData.getItemAt(i).uri
                    }
                }
                if (dataString != null)
                    results = arrayOf(Uri.parse(dataString))
            }
        }
        uploadMessageAboveL!!.onReceiveValue(results)
        uploadMessageAboveL = null
    }

    companion object {
        private val FILE_CHOOSER_RESULT_CODE = 10000
    }
}