preface
In Android audio and video development, online knowledge is too fragmented, self-learning is very difficult, but audio and video cattle Jhuster put forward “Android audio and video from the entry to improve – task list”. This article is the first Android audio and video task list, corresponding to the content to learn is: draw a picture on the Android platform, using at least three different API, ImageView, SurfaceView, custom View.
Audio and video task list
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directory
(1) ImageView draws pictures
(1) Put the pictures into MIpMAP-HDPI and Assets respectively
(2) Layout file:
<? xml version="1.0" encoding="utf-8"? > <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<ImageView
android:id="@+id/iv_picture"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</ImageView>
</LinearLayout>
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(3) Code:
// ImageView is loaded from several sources:
// (1)drawable/mipmap (r.drawabe. XXX
// (2) Assests path resources
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ImageView customImageView = findViewById(R.id.iv_picture);
Drawable /mipmap: use r.draabe. XXX to load image resources
// customImageView.setBackgroundResource(R.mipmap.wuqian);
// Method two: Load the assests path resources
customImageView.setImageBitmap(getImageFromAssetsFile(this."lilangdi.jpg"));
}
public static Bitmap getImageFromAssetsFile(Context context, String fileName) {
Bitmap image = null;
AssetManager am = context.getResources().getAssets();
try {
InputStream is = am.open(fileName);
image = BitmapFactory.decodeStream(is);
is.close();
} catch(IOException e) {
e.printStackTrace();
}
returnimage; }}Copy the code
(4) Results
(2) SurfaceView drawing pictures
(1) Put the picture in the mobile phone folder
(2) Layout:
<? xml version="1.0" encoding="utf-8"? > <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<SurfaceView
android:id="@+id/sv_drawpicture"
android:layout_width="match_parent"
android:layout_height="match_parent">
</SurfaceView>
</LinearLayout>
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(3) Add permissions
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
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(4) Code:
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
verifyStoragePermissions(this);
setContentView(R.layout.activity_main);
SurfaceView mSurfaceView = findViewById(R.id.sv_drawpicture);
mSurfaceView.getHolder().addCallback(new SurfaceHolder.Callback() {
@Override
public void surfaceCreated(SurfaceHolder holder) {
if (holder == null) {
return;
}
Paint paint = new Paint();
paint.setAntiAlias(true);
paint.setStyle(Paint.Style.STROKE);
/ / a: Environment. External.getexternalstoragedirectory () getPath () access path is: / storage/emulated / 0
Separator gets: /
Bitmap bitmap = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory().getPath() + File.separator + "wuqian.jpg"); / / get the bitmap
// Method 2:
// Bitmap bitmap = BitmapFactory.decodeFile("/storage/emulated/0/wuqian.jpg"); / / get the bitmap
Canvas canvas = holder.lockCanvas(); // Lock the canvas of the current surfaceView
canvas.drawBitmap(bitmap, 0.0, paint); // Perform the draw operation
holder.unlockCanvasAndPost(canvas); // Unlock it and display it on the interface
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}@Override
public void surfaceDestroyed(SurfaceHolder holder) {}}); }private static final int REQUEST_EXTERNAL_STORAGE = 1;
private static String[] PERMISSIONS_STORAGE = {
"android.permission.READ_EXTERNAL_STORAGE"."android.permission.WRITE_EXTERNAL_STORAGE" };
public static void verifyStoragePermissions(Activity activity) {
try {
// Check whether you have write permission
int permission = ActivityCompat.checkSelfPermission(activity,
"android.permission.WRITE_EXTERNAL_STORAGE");
if(permission ! = PackageManager.PERMISSION_GRANTED) {// There is no write permission. If you apply for the write permission, a dialog box will be displayedActivityCompat.requestPermissions(activity, PERMISSIONS_STORAGE,REQUEST_EXTERNAL_STORAGE); }}catch(Exception e) { e.printStackTrace(); }}}Copy the code
(5) Results
(3) Custom View drawing pictures
(1) Put the picture into the mobile phone or miPMAP-HDPI
(2) Layout:
<? xml version="1.0" encoding="utf-8"? > <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.lzacking.viewdemo.CustomView
android:id="@+id/customview"
android:layout_width="match_parent"
android:layout_height="match_parent">
</com.lzacking.viewdemo.CustomView>
</LinearLayout>
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(3) Add permissions
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
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(4) Code:
CustomView:
public class CustomView extends View {
Paint paint = new Paint();
Bitmap bitmap;
public CustomView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
paint.setAntiAlias(true);
paint.setStyle(Paint.Style.STROKE);
// Method 1: Read the image from the phone
bitmap = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory().getPath() + File.separator + "kugou.png"); / / get the bitmap
// Method 2: Read the image from mipmap-hdpi
// bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.taylor);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// It is not recommended to do any memory allocation in onDraw
if(bitmap ! =null) {
canvas.drawBitmap(bitmap, 0.0, paint); }}}Copy the code
MainActivity:
// Method 1: Read the image from the phone
// Method 2: Read the image from mipmap-hdpi
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// If you want to read pictures from your mobile phone, you need to apply for permission
verifyStoragePermissions(this);
setContentView(R.layout.activity_main);
}
private static final int REQUEST_EXTERNAL_STORAGE = 1;
private static String[] PERMISSIONS_STORAGE = {
"android.permission.READ_EXTERNAL_STORAGE"."android.permission.WRITE_EXTERNAL_STORAGE" };
public static void verifyStoragePermissions(Activity activity) {
try {
// Check whether you have write permission
int permission = ActivityCompat.checkSelfPermission(activity,
"android.permission.WRITE_EXTERNAL_STORAGE");
if(permission ! = PackageManager.PERMISSION_GRANTED) {// There is no write permission. If you apply for the write permission, a dialog box will be displayedActivityCompat.requestPermissions(activity, PERMISSIONS_STORAGE,REQUEST_EXTERNAL_STORAGE); }}catch(Exception e) { e.printStackTrace(); }}}Copy the code
(5) Results
Source code: Android audio and video development foundation (a) : through three ways (ImageView, SurfaceView, custom View) draw pictures