if (image.getDrawable().getConstantState().equals(getResources().getDrawable(0).getConstantState())){
image.setVisibility(View.GONE);
}else{
image.setVisibility(View.VISIBLE);
}
也就是说，如果图像没有任何可绘制图像，则图像将为GONE，否则为Visible。但是这段代码不起作用
答案 0 :(得分：1)
您可以在图像视图上调用getDrawable函数并检查它是否为空 - https://stackoverflow.com/a/16445086/1649353
答案 1 :(得分：0)
if (image.getDrawable().getConstantState().equals
(getResources().getDrawable(R.drawable.your_drawable).getConstantState()){//set here your drawable name(your_drawable)
image.setVisibility(View.VISIBLE);
}else{
image.setVisibility(View.GONE);
}
答案 2 :(得分：0)
事实上，还有另一种比较方式：
<!DOCTYPE html>
<meta charset="UTF-8">
<html>
<head>
<title>WebGL Cube with Texture</title>
<script type="x-shader/x-vertex" id="vshader">
attribute vec3 coords;
attribute vec2 texCoords;
uniform vec3 normal;
uniform mat4 modelview;
uniform mat4 projection;
uniform mat3 normalMatrix;
varying vec3 vNormal;
varying vec2 vTexCoords;
void main() {
vec4 coords = vec4(coords,1.0);
vec4 transformedVertex = modelview * coords;
vNormal = normalMatrix * normal;
vTexCoords = texCoords;
gl_Position = projection * transformedVertex;
}
</script>
<script type="x-shader/x-fragment" id="fshader">
precision mediump float;
uniform bool textured;
uniform sampler2D sampler;
varying vec3 vNormal;
varying vec2 vTexCoords;
uniform vec4 color;
void main() {
if (textured) {
vec4 color = texture2D(sampler, vTexCoords);
vec3 unitNormal = normalize(vNormal);
float multiplier = abs(unitNormal.z);
gl_FragColor = vec4( multiplier*color.r, multiplier*color.g, multiplier*color.b, color.a );
}
else {
gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0); // use basic white when texture's not there.
}
}
</script>
<script type="text/javascript" src="gl-matrix-min.js"></script>
<script type="text/javascript" src="simple-rotator.js"></script>
<script type="text/javascript">
"use strict";
var gl; // The webgl context.
var aCoords; // Location of the coords attribute variable in the shader program.
var aCoordsBuffer; // Buffer to hold coords.
var aTexCoords; // Location of the texCoords attribute variable in the shader program.
var aTexCoordsBuffer; // Buffer to hold texCoords.
var uProjection; // Location of the projection uniform matrix in the shader program.
var uModelview; // Location of the modelview unifirm matrix in the shader program.
var uNormal; // Location of the normal uniform in the shader program.
var uColor; // Location of the color uniform in the shader program, used only for axes.
var uTextured; // Location of the textured uniform in the shader program.
var uSampler; // Location of the sampler in the shader program.
var uNormalMatrix; // Location of the normalMatrix uniform matrix in the shader program.
var projection = mat4.create(); // projection matrix
var modelview = mat4.create(); // modelview matrix
var normalMatrix = mat3.create(); // matrix, derived from modelview matrix, for transforming normal vectors
var rotator; // A SimpleRotator object to enable rotation by mouse dragging.
var textureID = null; // Texture object, to be created after image has loaded.
/* Draws a colored cube, along with a set of coordinate axes.
* (Note that the use of the above drawPrimitive function is not an efficient
* way to draw with WebGL. Here, the geometry is so simple that it doesn't matter.)
*/
function draw() {
gl.clearColor(0,0,0,1);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
if (document.getElementById("persproj").checked) {
mat4.perspective(projection, Math.PI/4, 1, 2, 10);
}
else {
mat4.ortho(projection,-2.5, 2.5, -2.5, 2.5, 2, 10);
}
gl.uniformMatrix4fv(uProjection, false, projection );
var modelview = rotator.getViewMatrix();
var saveModelview = mat4.clone(modelview);
if (textureID) {
gl.uniform1i( uTextured, 1 ); // Tell shader to use texture and lighting.
gl.bindTexture(gl.TEXTURE_2D, textureID); // Which texture should be used.
gl.uniform1i(uSampler, 0); // Set sampler in shadre to use texture unit zero.
}
else {
gl.uniform1i( uTextured, 0 ); // Cube will appear in plain white.
}
drawFace(modelview) // front face of the cube
mat4.rotateY(modelview,modelview,Math.PI/2); //right face
drawFace(modelview) // front face
mat4.rotateY(modelview,modelview,Math.PI/2); //back face
drawFace(modelview) // front face
mat4.rotateY(modelview,modelview,Math.PI/2); //left face
drawFace(modelview) // front face
modelview = mat4.clone(saveModelview);
mat4.rotateX(modelview,modelview,Math.PI/2);
drawFace(modelview) // top face
mat4.rotateX(modelview,modelview,Math.PI);
drawFace(modelview) // bottom face
}
/**
* Draws the front face of the cube, subject to a modelview transform.
*/
function drawFace(modelview) {
gl.uniformMatrix4fv(uModelview, false, modelview );
mat3.normalFromMat4(normalMatrix, modelview);
gl.uniformMatrix3fv(uNormalMatrix, false, normalMatrix);
gl.uniform3f(uNormal, 0, 0, 1);
gl.drawArrays(gl.TRIANGLE_FAN, 0, 4); // front face
}
/**
* Loads data for the front face of the cube into VBOs.
*/
function createFace() {
var vertices = [ -1,-1,1, 1,-1,1, 1,1,1, -1,1,1 ];
var texCoords = [ 0,0, 2,0, 2,2, 0,2 ];
gl.enableVertexAttribArray(aCoords);
gl.bindBuffer(gl.ARRAY_BUFFER,aCoordsBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
gl.vertexAttribPointer(aCoords, 3, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(aTexCoords);
gl.bindBuffer(gl.ARRAY_BUFFER,aTexCoordsBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(texCoords), gl.STATIC_DRAW);
gl.vertexAttribPointer(aTexCoords, 2, gl.FLOAT, false, 0, 0);
}
/**
* Load an image from the URL "textures/bridk001.jpg". The image is loade
* asynchronously. When the
*/
function loadTexture() {
var img = new Image();
img.onload = function() {
var id = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D,id);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, img);
gl.generateMipmap(gl.TEXTURE_2D);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT);
textureID = id;
draw();
}
img.src = "./skin.jpg";
}
/* Creates a program for use in the WebGL context gl, and returns the
* identifier for that program. If an error occurs while compiling or
* linking the program, an exception of type String is thrown. The error
* string contains the compilation or linking error. If no error occurs,
* the program identifier is the return value of the function.
*/
function createProgram(gl, vertexShaderSource, fragmentShaderSource) {
var vsh = gl.createShader( gl.VERTEX_SHADER );
gl.shaderSource(vsh,vertexShaderSource);
gl.compileShader(vsh);
if ( ! gl.getShaderParameter(vsh, gl.COMPILE_STATUS) ) {
throw "Error in vertex shader: " + gl.getShaderInfoLog(vsh);
}
var fsh = gl.createShader( gl.FRAGMENT_SHADER );
gl.shaderSource(fsh, fragmentShaderSource);
gl.compileShader(fsh);
if ( ! gl.getShaderParameter(fsh, gl.COMPILE_STATUS) ) {
throw "Error in fragment shader: " + gl.getShaderInfoLog(fsh);
}
var prog = gl.createProgram();
gl.attachShader(prog,vsh);
gl.attachShader(prog, fsh);
gl.linkProgram(prog);
if ( ! gl.getProgramParameter( prog, gl.LINK_STATUS) ) {
throw "Link error in program: " + gl.getProgramInfoLog(prog);
}
return prog;
}
/* Gets the text content of an HTML element. This is used
* to get the shader source from the script elements that contain
* it. The parameter should be the id of the script element.
*/
function getTextContent( elementID ) {
var element = document.getElementById(elementID);
var fsource = "";
var node = element.firstChild;
var str = "";
while (node) {
if (node.nodeType == 3) // this is a text node
str += node.textContent;
node = node.nextSibling;
}
return str;
}
/**
* Initializes the WebGL program including the relevant global variables
* and the WebGL state. Creates a SimpleView3D object for viewing the
* cube and installs a mouse handler that lets the user rotate the cube.
*/
function init() {
try {
var canvas = document.getElementById("glcanvas");
gl = canvas.getContext("webgl");
if ( ! gl ) {
gl = canvas.getContext("experimental-webgl");
}
if ( ! gl ) {
throw "Could not create WebGL context.";
}
var vertexShaderSource = getTextContent("vshader");
var fragmentShaderSource = getTextContent("fshader");
var prog = createProgram(gl,vertexShaderSource,fragmentShaderSource);
gl.useProgram(prog);
aCoords = gl.getAttribLocation(prog, "coords");
aTexCoords = gl.getAttribLocation(prog, "texCoords");
uModelview = gl.getUniformLocation(prog, "modelview");
uProjection = gl.getUniformLocation(prog, "projection");
uSampler = gl.getUniformLocation(prog, "sampler");
uNormal = gl.getUniformLocation(prog, "normal");
uColor = gl.getUniformLocation(prog, "color");
uTextured = gl.getUniformLocation(prog, "textured");
uNormalMatrix = gl.getUniformLocation(prog, "normalMatrix");
aCoordsBuffer = gl.createBuffer();
aTexCoordsBuffer = gl.createBuffer();
gl.enable(gl.DEPTH_TEST);
gl.enable(gl.CULL_FACE); // no need to draw back faces
document.getElementById("persproj").checked = true;
rotator = new SimpleRotator(canvas,draw);
rotator.setView( [2,2,5], [0,1,0], 6 );
}
catch (e) {
document.getElementById("message").innerHTML =
"Could not initialize WebGL: " + e;
return;
}
createFace();
loadTexture();
draw();
}
</script>
</head>
<body onload="init()" style="background-color:#DDD">
<h2>A Cube With a Brick Texture</h2>
<p id=message>Drag the mouse on the canvas to rotate the view.</p>
<p>
<input type="radio" name="projectionType" id="persproj" value="perspective" onchange="draw()">
<label for="persproj">Perspective projection</label>
<input type="radio" name="projectionType" id="orthproj" value="orthogonal" onchange="draw()" style="margin-left:1cm">
<label for="orthproj">Orthogonal projection</label>
<button onclick="rotator.setView( [2,2,5], [0,1,0], 6 ); draw()" style="margin-left:1cm">Reset View</button>
</p>
<noscript><hr><h3>This page requires Javascript and a web browser that supports WebGL</h3><hr></noscript>
<div>
<canvas width=600 height=600 id="glcanvas" style="background-color:red"></canvas>
</div>
</body>
</html>
答案 3 :(得分：0)
if(imageview.getDrawable()==null)
{
//if Image View is Null
}
检查source
答案 4 :(得分：0)
尝试以下可能对你有用（这对我有用）
if(android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
if (image.getDrawable().getConstantState().equals(image.getContext().getDrawable(R.drawable.shadow_round_white).getConstantState())){
image.setVisibility(View.GONE);
}
else{
image.setVisibility(View.VISIBLE);
}
}
else {
if (image.getDrawable().getConstantState().equals(getResources().getDrawable(R.drawable.shadow_round_white).getConstantState())){
image.setVisibility(View.GONE);
}
else{
image.setVisibility(View.VISIBLE);
}
}