安卓开发问题汇总

Unexpected lock protocol found in lock file. Expected 3, found 37.

错误描述 在项目构建时报错：Unexpected lock protocol found in lock file. Expected 3, found 37.

原因 通常是Android Studio或电脑意外关闭引起的，具体原理未知。

解决方法 删除C盘用户目录下的.gradle文件，重启Android Studio。

TextView解决中英文混排自动换行

解决办法：自定义TextView解决中英文混排自动换行

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.text.Layout;
import android.text.StaticLayout;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.widget.TextView;

/**
 *  
 */
public class JustifyTextView extends TextView {

    private int mLineY;
    private int mViewWidth;
    public static final String TWO_CHINESE_BLANK = "  ";

    public JustifyTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right,
            int bottom) {
        super.onLayout(changed, left, top, right, bottom);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        TextPaint paint = getPaint();
        paint.setColor(getCurrentTextColor());
        paint.drawableState = getDrawableState();
        mViewWidth = getMeasuredWidth();
        String text = getText().toString();
        mLineY = 0;
        mLineY += getTextSize();
        Layout layout = getLayout();

        // layout.getLayout()在4.4.3出现NullPointerException
        if (layout == null) {
            return;
        }

        Paint.FontMetrics fm = paint.getFontMetrics();

        int textHeight = (int) (Math.ceil(fm.descent - fm.ascent));
        textHeight = (int) (textHeight * layout.getSpacingMultiplier() + layout
                .getSpacingAdd());
        //解决了最后一行文字间距过大的问题
        for (int i = 0; i < layout.getLineCount(); i++) {
            int lineStart = layout.getLineStart(i);
            int lineEnd = layout.getLineEnd(i);
            float width = StaticLayout.getDesiredWidth(text, lineStart,
                    lineEnd, getPaint());
            String line = text.substring(lineStart, lineEnd);

            if(i < layout.getLineCount() - 1) {
                if (needScale(line)) {
                    drawScaledText(canvas, lineStart, line, width);
                } else {
                    canvas.drawText(line, 0, mLineY, paint);
                }
            } else {
                canvas.drawText(line, 0, mLineY, paint);
            }
            mLineY += textHeight;
        }
    }

    private void drawScaledText(Canvas canvas, int lineStart, String line,
            float lineWidth) {
        float x = 0;
        if (isFirstLineOfParagraph(lineStart, line)) {
            String blanks = "  ";
            canvas.drawText(blanks, x, mLineY, getPaint());
            float bw = StaticLayout.getDesiredWidth(blanks, getPaint());
            x += bw;

            line = line.substring(3);
        }

        int gapCount = line.length() - 1;
        int i = 0;
        if (line.length() > 2 && line.charAt(0) == 12288
                && line.charAt(1) == 12288) {
            String substring = line.substring(0, 2);
            float cw = StaticLayout.getDesiredWidth(substring, getPaint());
            canvas.drawText(substring, x, mLineY, getPaint());
            x += cw;
            i += 2;
        }

        float d = (mViewWidth - lineWidth) / gapCount;
        for (; i < line.length(); i++) {
            String c = String.valueOf(line.charAt(i));
            float cw = StaticLayout.getDesiredWidth(c, getPaint());
            canvas.drawText(c, x, mLineY, getPaint());
            x += cw + d;
        }
    }

    private boolean isFirstLineOfParagraph(int lineStart, String line) {
        return line.length() > 3 && line.charAt(0) == ' '
                && line.charAt(1) == ' ';
    }

    private boolean needScale(String line) {
        if (line == null || line.length() == 0) {
            return false;
        } else {
            return line.charAt(line.length() - 1) != '\n';
        }
    }

}

使用

<com.hxtx.august.tools.JustifyTextView  
android:id="@+id/tv_fm_ftp_path"  
android:layout_width="wrap_content"  
android:layout_height="wrap_content"  
android:gravity="center_vertical"  
android:layout_marginStart="15dp"  
android:layout_marginEnd="15dp"  
android:text="路径:"  
android:textSize="15sp"  
tools:ignore="RtlSymmetry" />

listview的item的点击事件与checkbox点击时间冲突

设置checkbox属性

android:focusable="false" //因为checkBox的点击事件优先级高于listview的点击事件

<CheckBox  
    android:id="@+id/cb_folder_content_checkBox"  
    android:button="@null"  
    android:layout_width="24dp"  
    android:layout_height="24dp"  
    android:focusable="false"  
    android:background="@drawable/check_style"  
/>

APP本地下载文件出错

java.lang.RuntimeException: java.nio.file.NoSuchFileException: /data/user/0/com.hxtx.august/files/FTPData/README.md

这是因为没有找到这个路径和文件，应该判断一下有没有这个文件夹

File localFolder = new File(androidAppUrl + "/FTPData");  
if (!localFolder.exists()) {  
    localFolder.mkdirs();  
}

开子线程

// 需要执行一个方法
private void FtpDown(){
    // 开启一个子线程，进行网络操作，等待有返回结果，使用handler通知UI
    new Thread(networkTask).start();
}

// 在线程中写逻辑
Runnable networkTask = new Runnable() {
    @Override
    public void run() {
        try {
            String download = FileUtils.GetFtpPath(FtpActivity.this);
            downloadTv.setText("下载中...");
            // 回调成功
            Message msg = Message.obtain();
            msg.what = 1;
            msg.obj = e;
            handler.sendMessage(msg);
            // 如果传递数据可以这么写，result 是一个数据（对象或者列表）
            Message message = handler.obtainMessage(0x001, fileContent);
            handler.sendMessage(message);
        }catch (Exception e){
            // 回调失败
            Log.e(TAG,"出现异常----->>"+e.getMessage());
            Message msg = Message.obtain();
            msg.what = 1;
            msg.obj = e.getMessage();
            handler.sendMessage(msg);
            // 也可以这么写
            handler.sendEmptyMessage(0x002);
        }
    }
}

//用来接收子线程回调的结果
Handler handler = new Handler(Looper.getMainLooper()) {
    @Override
    public void handleMessage(Message msg) {
        super.handleMessage(msg);
        // 如果传递的是数据，则需要这么解析
        List<String> fileContent = (List<String>) msg.obj;
        
        switch (msg.what) {
            case 1://异常
                String error = (String) msg.obj;
                downloadTv.setText("出现异常-->"+error);
                break;
            case 2://成功
                String result = (String) msg.obj;
                downloadTv.setText(result);
                break;
        }
    }
};

页面跳转并传递数据

传递字符串

发送页面

Intent TestWifiIntent = new Intent(FtpManageAction.this, SinglePageAction.class);  
TestWifiIntent.putExtra("UrlData","file:///storage/emulated/0/Download/sample.csv");  
startActivity(TestWifiIntent);

接受页面

Intent intent = getIntent();//获取intent对象
String csvFilePath = intent.getStringExtra("UrlData");

当路径包含中文时，FTP读取FTP服务器列表出问题

解决办法:将路径转换为ISO-8859-1编码

String isoPath = new String(path.getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1);  
FTPFile[] files = ftpClient.listFiles(isoPath);

读取FTP内容，带进度

// 进度  
long step = ftpFile.getSize() / 100;  
long process = 0;  
long currentSize = 0;  
byte[] b = new byte[1024];  
int length;  
InputStream inputStream = ftpClient.retrieveFileStream(currentPath);  
if(inputStream!=null){  
    while ((length = inputStream.read(b)) != -1) {  
        // 下载文件  
        buffOut.write(b, 0, length);  
        currentSize = currentSize + length;  
        if (currentSize / step != process) {  
            process = currentSize / step;  
            //每隔%5的进度返回一次  
            if (process % 5 == 0) {  
                Log.d("IVESTAG", "ftp文件正在下载: "+process);  
            }  
        }  
    }  
    Message msg = Message.obtain();  
    msg.what = 1;  
    msg.obj = localFolder;  
    handlerFTPDownloadSingleData.sendMessage(msg);  
    // 关闭文件流  
    buffOut.close();  
    inputStream.close();  
    // 此方法是来确保流处理完毕，如果没有此方法，可能会造成现程序死掉  
    // if (ftpClient.completePendingCommand()) {  
    // Log.d("IVESTAG", "1ftp文件下载成功: "+ new File(localPath));  
    // } else {  
    // Log.d("IVESTAG", "2ftp文件下载失败: ");  
    // }
} else {  
    Message msg = Message.obtain();  
    msg.what = 0;  
    msg.obj = "文件空，未读到数据";  
    handlerFTPDownloadSingleData.sendMessage(msg);  
}

问题记录

open failed: EISDIR (Is a directory)

操作错误，这是一个文件夹而不是一个文件。

open failed: EEXIST (File exists)

安卓Android的Textview显示问题：一行没显示满就换行

设置Textview的属性android:breakStrategy为simple

<TextView  
    android:id="@+id/tv_folder_content_item_name"  
    android:layout_width="match_parent"  
    android:layout_height="wrap_content"  
    android:gravity="center_vertical"  
    android:breakStrategy="simple"  
    android:text="文本框"  
    android:textSize="15sp"
/>

预览CSV文件

// 浏览器预览
Intent TestWifiIntent = new Intent(FtpManageAction.this, SinglePageAction.class);  
TestWifiIntent.putExtra("UrlData",localFile);  
startActivity(TestWifiIntent);  

// WPS预览
Uri file = FileProvider.getUriForFile(FtpManageAction.this, "com.hxtx.august.fileprovider", localFile);  
Intent intent = new Intent();  
List<ResolveInfo> resInfoList = getPackageManager().queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY);  
for (ResolveInfo resolveInfo : resInfoList) {  
    String packageName = resolveInfo.activityInfo.packageName;  
    grantUriPermission(packageName, file, Intent.FLAG_GRANT_READ_URI_PERMISSION);  
}  
intent.setAction(Intent.ACTION_VIEW);  
String mimeType = MimeTypeMap.getSingleton().getMimeTypeFromExtension(MimeTypeMap.getFileExtensionFromUrl(file.toString()));  
intent.setDataAndType(file, mimeType);  
startActivity(intent);

数据类型转换

// 字符串转换为长整型（long）
String str = "12345";
long num = Long.parseLong(str);
System.out.println(num);
 
 // 字符串转换为长整型（long）
String str = "12345";
long num = Long.parseLong(str);
System.out.println(num);

// 字符串分割
String str = "apple/banana/cherry";
String[] parts = str.split("/");
for (String part : parts){
    System.out.println(part);
}