Android开发笔记（二十五）assets目录下的文件读取

import java.io.IOException;
import java.io.InputStream;

import com.example.exmassets.R;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends Activity implements OnClickListener {
	private final String TAG = "MainActivity";

	private TextView tvHint;
	private TextView tvTxt;
	private ImageView ivImg;
	private WebView wvHtm;
	private String fileName;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		tvHint = (TextView) findViewById(R.id.tvHint);
		tvTxt = (TextView) findViewById(R.id.tvTxt);
		ivImg = (ImageView) findViewById(R.id.ivImg);
		wvHtm = (WebView) findViewById(R.id.wvHtm);
		
		Button btn_txt = (Button) findViewById(R.id.btn_txt);
		Button btn_img = (Button) findViewById(R.id.btn_img);
		Button btn_htm = (Button) findViewById(R.id.btn_htm);
		btn_txt.setOnClickListener(this);
		btn_img.setOnClickListener(this);
		btn_htm.setOnClickListener(this);

		tvHint.setVisibility(View.VISIBLE);
		try {
			String[] fileNames = getAssets().list("");
			if (fileNames != null) {
				String fileDesc = String.format("assets根目录下找到%d个文件（夹）：", fileNames.length);
				for (int i=0; i<fileNames.length; i++) {
					if (i != 0) {
						fileDesc = fileDesc + "、";
					}
					fileDesc = fileDesc + fileNames[i];
				}
				fileDesc = fileDesc + "。";
				tvHint.setText(fileDesc);
			} else {
				tvHint.setText("assets根目录下没有找到任何文件（夹）。");
			}
			Log.d(TAG, String.format("assets根目录下找到%d个文件（夹）：", fileNames.length));
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	private String getTxtFromAssets(String fileName) {
		String result = "";
		try {
			InputStream is = getAssets().open(fileName);
			int lenght = is.available();
			byte[]  buffer = new byte[lenght];
			is.read(buffer);
			result = new String(buffer, "utf8");
		} catch (Exception e) {
			e.printStackTrace();
		}
		return result;
	}
	
	private Bitmap getImgFromAssets(String fileName) {
		Bitmap bitmap = null;
		try {
			InputStream is = getAssets().open(fileName);
			bitmap = BitmapFactory.decodeStream(is);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return bitmap;
	}

	@Override
	public void onClick(View v) {
		if (v.getId() == R.id.btn_txt) {
			fileName = "txt/libai.txt";
			tvHint.setText("当前打开的文本文件名是："+fileName);
			tvTxt.setVisibility(View.VISIBLE);
			ivImg.setVisibility(View.GONE);
			wvHtm.setVisibility(View.GONE);
			tvTxt.setText(getTxtFromAssets(fileName));
		} else if (v.getId() == R.id.btn_img) {
			fileName = "images/water.jpg";
			tvHint.setText("当前打开的图像文件名是："+fileName);
			tvTxt.setVisibility(View.GONE);
			ivImg.setVisibility(View.VISIBLE);
			wvHtm.setVisibility(View.GONE);
			ivImg.setImageBitmap(getImgFromAssets(fileName));
		} else if (v.getId() == R.id.btn_htm) {
			fileName = "file:///android_asset/html/index.html";
			tvHint.setText("当前打开的网页文件名是："+fileName);
			tvTxt.setVisibility(View.GONE);
			ivImg.setVisibility(View.GONE);
			wvHtm.setVisibility(View.VISIBLE);
			wvHtm.loadUrl(fileName);
			wvHtm.setWebViewClient(mWebViewClient);
		}
	}
	private WebViewClient mWebViewClient = new WebViewClient();

}